commit ee1fee90 upstream.

Setting PTRACE_O_SUSPEND_SECCOMP is supposed to be a highly privileged
operation because it allows the tracee to completely bypass all seccomp
filters on kernels with CONFIG_CHECKPOINT_RESTORE=y. It is only supposed to
be settable by a process with global CAP_SYS_ADMIN, and only if that
process is not subject to any seccomp filters at all.

However, while these permission checks were done on the PTRACE_SETOPTIONS
path, they were missing on the PTRACE_SEIZE path, which also sets
user-specified ptrace flags.

Move the permissions checks out into a helper function and let both
ptrace_attach() and ptrace_setoptions() call it.

Cc: stable@kernel.org
Fixes: 13c4a901

 ("seccomp: add ptrace options for suspend/resume")
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lkml.kernel.org/r/20220319010838.1386861-1-jannh@google.com

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The code is totally redundant remove it.

Link: https://lkml.kernel.org/r/20220103213312.9144-6-ebiederm@xmission.com

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Change the type and name of task_struct::state. Drop the volatile and
shrink it to an 'unsigned int'. Rename it in order to find all uses
such that we can use READ_ONCE/WRITE_ONCE as appropriate.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20210611082838.550736351@infradead.org

Suppose we have 2 threads, the group-leader L and a sub-theread T,
both parked in ptrace_stop(). Debugger tries to resume both threads
and does

	ptrace(PTRACE_CONT, T);
	ptrace(PTRACE_CONT, L);

If the sub-thread T execs in between, the 2nd PTRACE_CONT doesn not
resume the old leader L, it resumes the post-exec thread T which was
actually now stopped in PTHREAD_EVENT_EXEC. In this case the
PTHREAD_EVENT_EXEC event is lost, and the tracer can't know that the
tracee changed its pid.

This patch makes ptrace() fail in this case until debugger does wait()
and consumes PTHREAD_EVENT_EXEC which reports old_pid. This affects all
ptrace requests except the "asynchronous" PTRACE_INTERRUPT/KILL.

The patch doesn't add the new PTRACE_ option to not complicate the API,
and I _hope_ this won't cause any noticeable regression:

	- If debugger uses PTRACE_O_TRACEEXEC and the thread did an exec
	  and the tracer does a ptrace request without having consumed
	  the exec event, it's 100% sure that the thread the ptracer
	  thinks it is targeting does not exist anymore, or isn't the
	  same as the one it thinks it is targeting.

	- To some degree this patch adds nothing new. In the scenario
	  above ptrace(L) can fail with -ESRCH if it is called after the
	  execing sub-thread wakes the leader up and before it "steals"
	  the leader's pid.

Test-case:

	#include <stdio.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sys/ptrace.h>
	#include <sys/wait.h>
	#include <errno.h>
	#include <pthread.h>
	#include <assert.h>

	void *tf(void *arg)
	{
		execve("/usr/bin/true", NULL, NULL);
		assert(0);

		return NULL;
	}

	int main(void)
	{
		int leader = fork();
		if (!leader) {
			kill(getpid(), SIGSTOP);

			pthread_t th;
			pthread_create(&th, NULL, tf, NULL);
			for (;;)
				pause();

			return 0;
		}

		waitpid(leader, NULL, WSTOPPED);

		ptrace(PTRACE_SEIZE, leader, 0,
				PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXEC);
		waitpid(leader, NULL, 0);

		ptrace(PTRACE_CONT, leader, 0,0);
		waitpid(leader, NULL, 0);

		int status, thread = waitpid(-1, &status, 0);
		assert(thread > 0 && thread != leader);
		assert(status == 0x80137f);

		ptrace(PTRACE_CONT, thread, 0,0);
		/*
		 * waitid() because waitpid(leader, &status, WNOWAIT) does not
		 * report status. Why ????
		 *
		 * Why WEXITED? because we have another kernel problem connected
		 * to mt-exec.
		 */
		siginfo_t info;
		assert(waitid(P_PID, leader, &info, WSTOPPED|WEXITED|WNOWAIT) == 0);
		assert(info.si_pid == leader && info.si_status == 0x0405);

		/* OK, it sleeps in ptrace(PTRACE_EVENT_EXEC == 0x04) */
		assert(ptrace(PTRACE_CONT, leader, 0,0) == -1);
		assert(errno == ESRCH);

		assert(leader == waitpid(leader, &status, WNOHANG));
		assert(status == 0x04057f);

		assert(ptrace(PTRACE_CONT, leader, 0,0) == 0);

		return 0;
	}
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Simon Marchi <simon.marchi@efficios.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Pedro Alves <palves@redhat.com>
Acked-by: Simon Marchi <simon.marchi@efficios.com>
Acked-by: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This reverts commit 6fb8f43c

.

The IO threads do allow signals now, including SIGSTOP, and we can allow
ptrace attach. Attaching won't reveal anything interesting for the IO
threads, but it will allow eg gdb to attach to a task with io_urings
and IO threads without complaining. And once attached, it will allow
the usual introspection into regular threads.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

For userspace checkpoint and restore (C/R) a way of getting process state
containing RSEQ configuration is needed.

There are two ways this information is going to be used:
 - to re-enable RSEQ for threads which had it enabled before C/R
 - to detect if a thread was in a critical section during C/R

Since C/R preserves TLS memory and addresses RSEQ ABI will be restored
using the address registered before C/R.

Detection whether the thread is in a critical section during C/R is needed
to enforce behavior of RSEQ abort during C/R. Attaching with ptrace()
before registers are dumped itself doesn't cause RSEQ abort.
Restoring the instruction pointer within the critical section is
problematic because rseq_cs may get cleared before the control is passed
to the migrated application code leading to RSEQ invariants not being
preserved. C/R code will use RSEQ ABI address to find the abort handler
to which the instruction pointer needs to be set.

To achieve above goals expose the RSEQ ABI address and the signature value
with the new ptrace request PTRACE_GET_RSEQ_CONFIGURATION.

This new ptrace request can also be used by debuggers so they are aware
of stops within restartable sequences in progress.
Signed-off-by: Piotr Figiel <figiel@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michal Miroslaw <emmir@google.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20210226135156.1081606-1-figiel@google.com

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Despite a comment that said that page fault accounting would be charged to
whatever task_struct* was passed into __access_remote_vm(), the tsk
argument was actually unused.

Making page fault accounting actually use this task struct is quite a
project, so there is no point in keeping the tsk argument.

Delete both the comment, and the argument.

[rppt@linux.ibm.com: changelog addition]

Link: https://lkml.kernel.org/r/20201026074137.4147787-1-jhubbard@nvidia.com

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 69f594a3 ("ptrace: do not audit capability check when outputing
/proc/pid/stat") replaced the use of ns_capable() with
has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV.

Commit 6b3ad664 ("ptrace: reintroduce usage of subjective credentials in
ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with
security_capable(), which doesn't set PF_SUPERPRIV neither.

Since commit 98f368e9 ("kernel: Add noaudit variant of ns_capable()"), a
new ns_capable_noaudit() helper is available.  Let's use it!

As a result, the signature of ptrace_has_cap() is restored to its original one.

Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: stable@vger.kernel.org
Fixes: 6b3ad664 ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()")
Fixes: 69f594a3

 ("ptrace: do not audit capability check when outputing /proc/pid/stat")
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201030123849.770769-2-mic@digikod.net

On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_EMU, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-8-krisman@collabora.com

On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_TRACE, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-7-krisman@collabora.com

Commit 69f594a3

 ("ptrace: do not audit capability check when outputing /proc/pid/stat")
introduced the ability to opt out of audit messages for accesses to various
proc files since they are not violations of policy.  While doing so it
somehow switched the check from ns_capable() to
has_ns_capability{_noaudit}(). That means it switched from checking the
subjective credentials of the task to using the objective credentials. This
is wrong since. ptrace_has_cap() is currently only used in
ptrace_may_access() And is used to check whether the calling task (subject)
has the CAP_SYS_PTRACE capability in the provided user namespace to operate
on the target task (object). According to the cred.h comments this would
mean the subjective credentials of the calling task need to be used.
This switches ptrace_has_cap() to use security_capable(). Because we only
call ptrace_has_cap() in ptrace_may_access() and in there we already have a
stable reference to the calling task's creds under rcu_read_lock() there's
no need to go through another series of dereferences and rcu locking done
in ns_capable{_noaudit}().

As one example where this might be particularly problematic, Jann pointed
out that in combination with the upcoming IORING_OP_OPENAT feature, this
bug might allow unprivileged users to bypass the capability checks while
asynchronously opening files like /proc/*/mem, because the capability
checks for this would be performed against kernel credentials.

To illustrate on the former point about this being exploitable: When
io_uring creates a new context it records the subjective credentials of the
caller. Later on, when it starts to do work it creates a kernel thread and
registers a callback. The callback runs with kernel creds for
ktask->real_cred and ktask->cred. To prevent this from becoming a
full-blown 0-day io_uring will call override_cred() and override
ktask->cred with the subjective credentials of the creator of the io_uring
instance. With ptrace_has_cap() currently looking at ktask->real_cred this
override will be ineffective and the caller will be able to open arbitray
proc files as mentioned above.
Luckily, this is currently not exploitable but will turn into a 0-day once
IORING_OP_OPENAT{2} land in v5.6. Fix it now!

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Jann Horn <jannh@google.com>
Fixes: 69f594a3

 ("ptrace: do not audit capability check when outputing /proc/pid/stat")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

PTRACE_GET_SYSCALL_INFO is a generic ptrace API that lets ptracer obtain
details of the syscall the tracee is blocked in.

There are two reasons for a special syscall-related ptrace request.

Firstly, with the current ptrace API there are cases when ptracer cannot
retrieve necessary information about syscalls.  Some examples include:

 * The notorious int-0x80-from-64-bit-task issue. See [1] for details.
   In short, if a 64-bit task performs a syscall through int 0x80, its
   tracer has no reliable means to find out that the syscall was, in
   fact, a compat syscall, and misidentifies it.

 * Syscall-enter-stop and syscall-exit-stop look the same for the
   tracer. Common practice is to keep track of the sequence of
   ptrace-stops in order not to mix the two syscall-stops up. But it is
   not as simple as it looks; for example, strace had a (just recently
   fixed) long-standing bug where attaching strace to a tracee that is
   performing the execve system call led to the tracer identifying the
   following syscall-exit-stop as syscall-enter-stop, which messed up
   all the state tracking.

 * Since the introduction of commit 84d77d3f ("ptrace: Don't allow
   accessing an undumpable mm"), both PTRACE_PEEKDATA and
   process_vm_readv become unavailable when the process dumpable flag is
   cleared. On such architectures as ia64 this results in all syscall
   arguments being unavailable for the tracer.

Secondly, ptracers also have to support a lot of arch-specific code for
obtaining information about the tracee.  For some architectures, this
requires a ptrace(PTRACE_PEEKUSER, ...) invocation for every syscall
argument and return value.

ptrace(2) man page:

long ptrace(enum __ptrace_request request, pid_t pid,
            void *addr, void *data);
...
PTRACE_GET_SYSCALL_INFO
       Retrieve information about the syscall that caused the stop.
       The information is placed into the buffer pointed by "data"
       argument, which should be a pointer to a buffer of type
       "struct ptrace_syscall_info".
       The "addr" argument contains the size of the buffer pointed to
       by "data" argument (i.e., sizeof(struct ptrace_syscall_info)).
       The return value contains the number of bytes available
       to be written by the kernel.
       If the size of data to be written by the kernel exceeds the size
       specified by "addr" argument, the output is truncated.

[ldv@altlinux.org: selftests/seccomp/seccomp_bpf: update for PTRACE_GET_SYSCALL_INFO]
  Link: http://lkml.kernel.org/r/20190708182904.GA12332@altlinux.org
Link: http://lkml.kernel.org/r/20190510152842.GF28558@altlinux.org

Signed-off-by: Elvira Khabirova <lineprinter@altlinux.org>
Co-developed-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Eugene Syromyatnikov <esyr@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Helge Deller <deller@gmx.de>	[parisc]
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: kbuild test robot <lkp@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vincent Chen <deanbo422@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix two issues:

When called for PTRACE_TRACEME, ptrace_link() would obtain an RCU
reference to the parent's objective credentials, then give that pointer
to get_cred().  However, the object lifetime rules for things like
struct cred do not permit unconditionally turning an RCU reference into
a stable reference.

PTRACE_TRACEME records the parent's credentials as if the parent was
acting as the subject, but that's not the case.  If a malicious
unprivileged child uses PTRACE_TRACEME and the parent is privileged, and
at a later point, the parent process becomes attacker-controlled
(because it drops privileges and calls execve()), the attacker ends up
with control over two processes with a privileged ptrace relationship,
which can be abused to ptrace a suid binary and obtain root privileges.

Fix both of these by always recording the credentials of the process
that is requesting the creation of the ptrace relationship:
current_cred() can't change under us, and current is the proper subject
for access control.

This change is theoretically userspace-visible, but I am not aware of
any code that it will actually break.

Fixes: 64b875f7

 ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Restore the read memory barrier in __ptrace_may_access() that was deleted
a couple years ago. Also add comments on this barrier and the one it pairs
with to explain why they're there (as far as I understand).

Fixes: bfedb589

 ("mm: Add a user_ns owner to mm_struct and fix ptrace permission checks")
Cc: stable@vger.kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

While the TIF_SYSCALL_EMU is set in ptrace_resume independent of any
architecture, currently only powerpc and x86 unset the TIF_SYSCALL_EMU
flag in ptrace_disable which gets called from ptrace_detach.

Let's move the clearing of TIF_SYSCALL_EMU flag to __ptrace_unlink
which gets executed from ptrace_detach and also keep it along with
or close to clearing of TIF_SYSCALL_TRACE.

Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Recently syzbot in conjunction with KMSAN reported that
ptrace_peek_siginfo can copy an uninitialized siginfo to userspace.
Inspecting ptrace_peek_siginfo confirms this.

The problem is that off when initialized from args.off can be
initialized to a negaive value.  At which point the "if (off >= 0)"
test to see if off became negative fails because off started off
negative.

Prevent the core problem by adding a variable found that is only true
if a siginfo is found and copied to a temporary in preparation for
being copied to userspace.

Prevent args.off from being truncated when being assigned to off by
testing that off is <= the maximum possible value of off.  Convert off
to an unsigned long so that we should not have to truncate args.off,
we have well defined overflow behavior so if we add another check we
won't risk fighting undefined compiler behavior, and so that we have a
type whose maximum value is easy to test for.

Cc: Andrei Vagin <avagin@gmail.com>
Cc: stable@vger.kernel.org
Reported-by: syzbot+0d602a1b0d8c95bdf299@syzkaller.appspotmail.com
Fixes: 84c751bd

 ("ptrace: add ability to retrieve signals without removing from a queue (v4)")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

There are a few system calls (pselect, ppoll, etc) which replace a task
sigmask while they are running in a kernel-space

When a task calls one of these syscalls, the kernel saves a current
sigmask in task->saved_sigmask and sets a syscall sigmask.

On syscall-exit-stop, ptrace traps a task before restoring the
saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and
PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by
saved_sigmask, when the task returns to user-space.

This patch fixes this problem.  PTRACE_GETSIGMASK returns saved_sigmask
if it's set.  PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Link: http://lkml.kernel.org/r/20181120060616.6043-1-avagin@gmail.com
Fixes: 29000cae

 ("ptrace: add ability to get/set signal-blocked mask")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.

It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access.  But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.

A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model.  And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.

This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.

There were a couple of notable cases:

 - csk...

The IBPB control code in x86 removed the usage. Remove the functionality
which was introduced for this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.559149393@linutronix.de

Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo.  Keeping the
traditional name for the userspace definition.  While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo.  The reduction in size comes in a following change.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

In preparation for using a smaller version of siginfo in the kernel
introduce copy_siginfo_from_user and use it when siginfo is copied from
userspace.

Make the pattern for using copy_siginfo_from_user and
copy_siginfo_from_user32 to capture the return value and return that
value on error.

This is a necessary prerequisite for using a smaller siginfo
in the kernel than the kernel exports to userspace.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Currently, IBPB is only issued in cases when switching into a non-dumpable
process, the rationale being to protect such 'important and security
sensitive' processess (such as GPG) from data leaking into a different
userspace process via spectre v2.

This is however completely insufficient to provide proper userspace-to-userpace
spectrev2 protection, as any process can poison branch buffers before being
scheduled out, and the newly scheduled process immediately becomes spectrev2
victim.

In order to minimize the performance impact (for usecases that do require
spectrev2 protection), issue the barrier only in cases when switching between
processess where the victim can't be ptraced by the potential attacker (as in
such cases, the attacker doesn't have to bother with branch buffers at all).

[ tglx: Split up PTRACE_MODE_NOACCESS_CHK into PTRACE_MODE_SCHED and
  PTRACE_MODE_IBPB to be able to do ptrace() context tracking reasonably
  fine-grained ]

Fixes: 18bf3c3e

 ("x86/speculation: Use Indirect Branch Prediction Barrier in context switch")
Originally-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc:  "WoodhouseDavid" <dwmw@amazon.co.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc:  "SchauflerCasey" <casey.schaufler@intel.com>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1809251437340.15880@cbobk.fhfr.pm

Now that siginfo is never allocated for SIGKILL and SIGSTOP there is
no difference between SEND_SIG_PRIV and SEND_SIG_FORCED for SIGKILL
and SIGSTOP.  This makes SEND_SIG_FORCED unnecessary and redundant in
the presence of SIGKILL and SIGSTOP.  Therefore change users of
SEND_SIG_FORCED that are sending SIGKILL or SIGSTOP to use
SEND_SIG_PRIV instead.

This removes the last users of SEND_SIG_FORCED.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

There are several functions that do find_task_by_vpid() followed by
get_task_struct().  We can use a helper function instead.

Link: http://lkml.kernel.org/r/1509602027-11337-1-git-send-email-rppt@linux.vnet.ibm.com

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Now that copy_siginfo copies all of the fields this is safe, safer (as
all of the bits are guaranteed to be copied), clearer, and less error
prone than using a structure copy.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

The new unified copy_siginfo_from_user32 takes care of this.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
flags for checkpoint restore, since they describe the state of a filter.

So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
returns the metadata of the nth filter (right now, just the flags).
Hopefully this will be future proof, and new per-filter metadata can be
added to this struct.
Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

struct siginfo is a union and the kernel since 2.4 has been hiding a union
tag in the high 16bits of si_code using the values:
__SI_KILL
__SI_TIMER
__SI_POLL
__SI_FAULT
__SI_CHLD
__SI_RT
__SI_MESGQ
__SI_SYS

While this looks plausible on the surface, in practice this situation has
not worked well.

- Injected positive signals are not copied to user space properly
  unless they have these magic high bits set.

- Injected positive signals are not reported properly by signalfd
  unless they have these magic high bits set.

- These kernel internal values leaked to userspace via ptrace_peek_siginfo

- It was possible to inject these kernel internal values and cause the
  the kernel to misbehave.

- Kernel developers got confused and expected these kernel internal values
  in userspace in kernel self tests.

- Kernel developers got confused and set si_code to __SI_FAULT which
  is SI_USER in userspace which causes userspace to think an ordinary user
  sent the signal and that it was not kernel generated.

- The values make it impossible to reorganize the code to transform
  siginfo_copy_to_user into a plain copy_to_user.  As si_code must
  be massaged before being passed to userspace.

So remove these kernel internal si codes and make the kernel code simpler
and more maintainable.

To replace these kernel internal magic si_codes introduce the helper
function siginfo_layout, that takes a signal number and an si_code and
computes which union member of siginfo is being used.  Have
siginfo_layout return an enumeration so that gcc will have enough
information to warn if a switch statement does not handle all of union
members.

A couple of architectures have a messed up ABI that defines signal
specific duplications of SI_USER which causes more special cases in
siginfo_layout than I would like.  The good news is only problem
architectures pay the cost.

Update all of the code that used the previous magic __SI_ values to
use the new SIL_ values and to call siginfo_layout to get those
values.  Escept where not all of the cases are handled remove the
defaults in the switch statements so that if a new case is missed in
the future the lack will show up at compile time.

Modify the code that copies siginfo si_code to userspace to just copy
the value and not cast si_code to a short first.  The high bits are no
longer used to hold a magic union member.

Fixup the siginfo header files to stop including the __SI_ values in
their constants and for the headers that were missing it to properly
update the number of si_codes for each signal type.

The fixes to copy_siginfo_from_user32 implementations has the
interesting property that several of them perviously should never have
worked as the __SI_ values they depended up where kernel internal.
With that dependency gone those implementations should work much
better.

The idea of not passing the __SI_ values out to userspace and then
not reinserting them has been tested with criu and criu worked without
changes.

Ref: 2.4.0-test1
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

When I introduced ptracer_cred I failed to consider the weirdness of
fork where the task_struct copies the old value by default.  This
winds up leaving ptracer_cred set even when a process forks and
the child process does not wind up being ptraced.

Because ptracer_cred is not set on non-ptraced processes whose
parents were ptraced this has broken the ability of the enlightenment
window manager to start setuid children.

Fix this by properly initializing ptracer_cred in ptrace_init_task

This must be done with a little bit of care to preserve the current value
of ptracer_cred when ptrace carries through fork.  Re-reading the
ptracer_cred from the ptracing process at this point is inconsistent
with how PT_PTRACE_CAP has been maintained all of these years.
Tested-by: Takashi Iwai <tiwai@suse.de>
Fixes: 64b875f7

 ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against
__TASK_TRACED.  If this races with the ptrace_unfreeze_traced at the end
of a PTRACE_LISTEN, this can wake the task /after/ the check against
__TASK_TRACED, but before the reset of state to TASK_TRACED.  This
causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup
against TRACED while the task is still on the rq wake_list, corrupting
it.

Oleg said:
 "The kernel can crash or this can lead to other hard-to-debug problems.
  In short, "task->state = TASK_TRACED" in ptrace_unfreeze_traced()
  assumes that nobody else can wake it up, but PTRACE_LISTEN breaks the
  contract. Obviusly it is very wrong to manipulate task->state if this
  task is already running, or WAKING, or it sleeps again"

[akpm@linux-foundation.org: coding-style fixes]
Fixes: 9899d11f ("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL")
Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com

Signed-off-by: Ben Segall <bsegall@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

We are going to split <linux/sched/coredump.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/coredump.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

We are going to split <linux/sched/mm.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/mm.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

The APIs that are going to be moved first are:

   mm_alloc()
   __mmdrop()
   mmdrop()
   mmdrop_async_fn()
   mmdrop_async()
   mmget_not_zero()
   mmput()
   mmput_async()
   get_task_mm()
   mm_access()
   mm_release()

Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

It is the reasonable expectation that if an executable file is not
readable there will be no way for a user without special privileges to
read the file.  This is enforced in ptrace_attach but if ptrace
is already attached before exec there is no enforcement for read-only
executables.

As the only way to read such an mm is through access_process_vm
spin a variant called ptrace_access_vm that will fail if the
target process is not being ptraced by the current process, or
the current process did not have sufficient privileges when ptracing
began to read the target processes mm.

In the ptrace implementations replace access_process_vm by
ptrace_access_vm.  There remain several ptrace sites that still use
access_process_vm as they are reading the target executables
instructions (for kernel consumption) or register stacks.  As such it
does not appear necessary to add a permission check to those calls.

This bug has always existed in Linux.

Fixes: v1.0
Cc: stable@vger.kernel.org
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

When the flag PT_PTRACE_CAP was added the PTRACE_TRACEME path was
overlooked.  This can result in incorrect behavior when an application
like strace traces an exec of a setuid executable.

Further PT_PTRACE_CAP does not have enough information for making good
security decisions as it does not report which user namespace the
capability is in.  This has already allowed one mistake through
insufficient granulariy.

I found this issue when I was testing another corner case of exec and
discovered that I could not get strace to set PT_PTRACE_CAP even when
running strace as root with a full set of caps.

This change fixes the above issue with strace allowing stracing as
root a setuid executable without disabling setuid.  More fundamentaly
this change allows what is allowable at all times, by using the correct
information in it's decision.

Cc: stable@vger.kernel.org
Fixes: 4214e42f96d4 ("v2.4.9.11 -> v2.4.9.12")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

During exec dumpable is cleared if the file that is being executed is
not readable by the user executing the file.  A bug in
ptrace_may_access allows reading the file if the executable happens to
enter into a subordinate user namespace (aka clone(CLONE_NEWUSER),
unshare(CLONE_NEWUSER), or setns(fd, CLONE_NEWUSER).

This problem is fixed with only necessary userspace breakage by adding
a user namespace owner to mm_struct, captured at the time of exec, so
it is clear in which user namespace CAP_SYS_PTRACE must be present in
to be able to safely give read permission to the executable.

The function ptrace_may_access is modified to verify that the ptracer
has CAP_SYS_ADMIN in task->mm->user_ns instead of task->cred->user_ns.
This ensures that if the task changes it's cred into a subordinate
user namespace it does not become ptraceable.

The function ptrace_attach is modified to only set PT_PTRACE_CAP when
CAP_SYS_PTRACE is held over task->mm->user_ns.  The intent of
PT_PTRACE_CAP is to be a flag to note that whatever permission changes
the task might go through the tracer has sufficient permissions for
it not to be an issue.  task->cred->user_ns is always the same
as or descendent of mm->user_ns.  Which guarantees that having
CAP_SYS_PTRACE over mm->user_ns is the worst case for the tasks
credentials.

To prevent regressions mm->dumpable and mm->user_ns are not considered
when a task has no mm.  As simply failing ptrace_may_attach causes
regressions in privileged applications attempting to read things
such as /proc/<pid>/stat

Cc: stable@vger.kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
Fixes: 8409cca7

 ("userns: allow ptrace from non-init user namespaces")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

This removes the 'write' argument from access_process_vm() and replaces
it with 'gup_flags' as use of this function previously silently implied
FOLL_FORCE, whereas after this patch callers explicitly pass this flag.

We make this explicit as use of FOLL_FORCE can result in surprising
behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

On __ptrace_detach(), called from do_exit()->exit_notify()->
forget_original_parent()->exit_ptrace(), the TIF_SYSCALL_TRACE in
thread->flags of the tracee is not cleared up.  This results in the
tracehook_report_syscall_* being called (though there's no longer a tracer
listening to that) upon its further syscalls.

Example scenario - attach "strace" to a running process and kill it (the
strace) with SIGKILL.  You'll see that the syscall trace hooks are still
being called.

The clearing of this flag should be moved from ptrace_detach() to
__ptrace_detach().

Link: http://lkml.kernel.org/r/1472759493-20554-1-git-send-email-alnovak@suse.cz

Signed-off-by: Ales Novak <alnovak@suse.cz>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>