- 18 Oct, 2020 1 commit
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Jann Horn authored
create_elf_tables() runs after setup_new_exec(), so other tasks can already access our new mm and do things like process_madvise() on it. (At the time I'm writing this commit, process_madvise() is not in mainline yet, but has been in akpm's tree for some time.) While I believe that there are currently no APIs that would actually allow another process to mess up our VMA tree (process_madvise() is limited to MADV_COLD and MADV_PAGEOUT, and uring and userfaultfd cannot reach an mm under which no syscalls have been executed yet), this seems like an accident waiting to happen. Let's make sure that we always take the mmap lock around GUP paths as long as another process might be able to see the mm. (Yes, this diff looks suspicious because we drop the lock before doing anything with `vma`, but that's because we actually don't do anything with it apart from the NULL check.) Signed-off-by:
Jann Horn <jannh@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Acked-by:
Michel Lespinasse <walken@google.com> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Sakari Ailus <sakari.ailus@linux.intel.com> Link: https://lkml.kernel.org/r/CAG48ez1-PBCdv3y8pn-Ty-b+FmBSLwDuVKFSt8h7wARLy0dF-Q@mail.gmail.com Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- 16 Oct, 2020 4 commits
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Jann Horn authored
In both binfmt_elf and binfmt_elf_fdpic, use a new helper dump_vma_snapshot() to take a snapshot of the VMA list (including the gate VMA, if we have one) while protected by the mmap_lock, and then use that snapshot instead of walking the VMA list without locking. An alternative approach would be to keep the mmap_lock held across the entire core dumping operation; however, keeping the mmap_lock locked while we may be blocked for an unbounded amount of time (e.g. because we're dumping to a FUSE filesystem or so) isn't really optimal; the mmap_lock blocks things like the ->release handler of userfaultfd, and we don't really want critical system daemons to grind to a halt just because someone "gifted" them SCM_RIGHTS to an eternally-locked userfaultfd, or something like that. Since both the normal ELF code and the FDPIC ELF code need this functionality (and if any other binfmt wants to add coredump support in the future, they'd probably need it, too), implement this with a common helper in fs/coredump.c. A downside of this approach is that we now need a bigger amount of kernel memory per userspace VMA in the normal ELF case, and that we need O(n) kernel memory in the FDPIC ELF case at all; but 40 bytes per VMA shouldn't be terribly bad. There currently is a data race between stack expansion and anything that reads ->vm_start or ->vm_end under the mmap_lock held in read mode; to mitigate that for core dumping, take the mmap_lock in write mode when taking a snapshot of the VMA hierarchy. (If we only took the mmap_lock in read mode, we could end up with a corrupted core dump if someone does get_user_pages_remote() concurrently. Not really a major problem, but taking the mmap_lock either way works here, so we might as well avoid the issue.) (This doesn't do anything about the existing data races with stack expansion in other mm code.) Signed-off-by:
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Jann Horn authored
At the moment, the binfmt_elf and binfmt_elf_fdpic code have slightly different code to figure out which VMAs should be dumped, and if so, whether the dump should contain the entire VMA or just its first page. Eliminate duplicate code by reworking the binfmt_elf version into a generic core dumping helper in coredump.c. As part of that, change the heuristic for detecting executable/library header pages to check whether the inode is executable instead of looking at the file mode. This is less problematic in terms of locking because it lets us avoid get_user() under the mmap_sem. (And arguably it looks nicer and makes more sense in generic code.) Adjust a little bit based on the binfmt_elf_fdpic version: ->anon_vma is only meaningful under CONFIG_MMU, otherwise we have to assume that the VMA has been written to. Suggested-by:
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Jann Horn authored
Both fs/binfmt_elf.c and fs/binfmt_elf_fdpic.c need to dump ranges of pages into the coredump file. Extract that logic into a common helper. Signed-off-by:
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Chris Kennelly authored
Patch series "Selecting Load Addresses According to p_align", v3. The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. While specifying -z,max-page-size=0x200000 to the linker will generate suitably aligned segments for huge pages on x86_64, the executable needs to be loaded at a suitably aligned address as well. This alignment requires the binary's cooperation, as distinct segments need to be appropriately paddded to be eligible for THP. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. This patch (of 2): The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. Tested by verifying program with -Wl,-z,max-page-size=0x200000 loading. [akpm@linux-foundation.org: fix max() warning] [ckennelly@google.com: augment comment] Link: https://lkml.kernel.org/r/20200821233848.3904680-2-ckennelly@google.com Signed-off-by:
Chris Kennelly <ckennelly@google.com> Signed-off-by:
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- 27 Jul, 2020 2 commits
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Al Viro authored
all uses are conditional upon ELF_CORE_COPY_XFPREGS, which has not been defined on any architecture since 2010 Signed-off-by:Al Viro <viro@zeniv.linux.org.uk>
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Al Viro authored
Two new helpers: given a process and regset, dump into a buffer. regset_get() takes a buffer and size, regset_get_alloc() takes size and allocates a buffer. Return value in both cases is the amount of data actually dumped in case of success or -E... on error. In both cases the size is capped by regset->n * regset->size, so ->get() is called with offset 0 and size no more than what regset expects. binfmt_elf.c callers of ->get() are switched to using those; the other caller (copy_regset_to_user()) will need some preparations to switch. Signed-off-by:
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- 05 Jun, 2020 1 commit
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Anthony Iliopoulos authored
The ifndef was added a long time ago to support archs that would define their own mapping function. The last user was the metag arch which was removed from the tree, and as such there are no users left. Let's kill it. Signed-off-by:
Anthony Iliopoulos <ailiop@suse.com> Signed-off-by:
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- 03 Jun, 2020 1 commit
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Al Viro authored
Signed-off-by:
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- 28 May, 2020 1 commit
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Alexander Potapenko authored
KMSAN reported uninitialized data being written to disk when dumping core. As a result, several kilobytes of kmalloc memory may be written to the core file and then read by a non-privileged user. Reported-by:
sam <sunhaoyl@outlook.com> Signed-off-by:
Alexander Potapenko <glider@google.com> Signed-off-by:
Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200419100848.63472-1-glider@google.com Link: https://github.com/google/kmsan/issues/76 Signed-off-by:
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- 21 May, 2020 1 commit
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Eric W. Biederman authored
Most of the support for passing the file descriptor of an executable to an interpreter already lives in the generic code and in binfmt_elf. Rework the fields in binfmt_elf that deal with executable file descriptor passing to make executable file descriptor passing a first class concept. Move the fd_install from binfmt_misc into begin_new_exec after the new creds have been installed. This means that accessing the file through /proc/<pid>/fd/N is able to see the creds for the new executable before allowing access to the new executables files. Performing the install of the executables file descriptor after the point of no return also means that nothing special needs to be done on error. The exiting of the process will close all of it's open files. Move the would_dump from binfmt_misc into begin_new_exec right after would_dump is called on the bprm->file. This makes it obvious this case exists and that no nesting of bprm->file is currently supported. In binfmt_misc the movement of fd_install into generic code means that it's special error exit path is no longer needed. Link: https://lkml.kernel.org/r/87y2poyd91.fsf_-_@x220.int.ebiederm.org Acked-by:
"Eric W. Biederman" <ebiederm@xmission.com>
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- 07 May, 2020 2 commits
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Eric W. Biederman authored
There is and has been for a very long time been a lot more going on in flush_old_exec than just flushing the old state. After the movement of code from setup_new_exec there is a whole lot more going on than just flushing the old executables state. Rename flush_old_exec to begin_new_exec to more accurately reflect what this function does. Reviewed-by:
Greg Ungerer <gerg@linux-m68k.org> Signed-off-by:
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Eric W. Biederman authored
The two functions are now always called one right after the other so merge them together to make future maintenance easier. Reviewed-by:
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- 05 May, 2020 2 commits
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Christoph Hellwig authored
There is no logic in elf_core_dump itself or in the various arch helpers called from it which use uaccess routines on kernel pointers except for the file writes thate are nicely encapsulated by using __kernel_write in dump_emit. Signed-off-by:
Christoph Hellwig <hch@lst.de> Signed-off-by:
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Eric W. Biederman authored
The code in binfmt_elf.c is differnt from the rest of the code that processes siginfo, as it sends siginfo from a kernel buffer to a file rather than from kernel memory to userspace buffers. To remove it's use of set_fs the code needs some different siginfo helpers. Add the helper copy_siginfo_to_external to copy from the kernel's internal siginfo layout to a buffer in the siginfo layout that userspace expects. Modify fill_siginfo_note to use copy_siginfo_to_external instead of set_fs and copy_siginfo_to_user. Update compat_binfmt_elf.c to use the previously added copy_siginfo_to_external32 to handle the compat case. Signed-off-by:
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- 07 Apr, 2020 4 commits
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Alexey Dobriyan authored
Static executables don't need to free NULL pointer. It doesn't matter really because static executable is not common scenario but do it anyway out of pedantry. Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:
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Alexey Dobriyan authored
PT_INTERP ELF header can be spared if executable is static. Signed-off-by:
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Alexey Dobriyan authored
"loc" variable became just a wrapper for PT_INTERP ELF header after main ELF header was moved to "bprm->buf". Delete it. Signed-off-by:
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Anshuman Khandual authored
This replaces all remaining open encodings with is_vm_hugetlb_page(). Signed-off-by:
Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by:
Vlastimil Babka <vbabka@suse.cz> Cc: Paul Mackerras <paulus@ozlabs.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Will Deacon <will@kernel.org> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Cc: Nick Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Guo Ren <guoren@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Paul Burton <paulburton@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Rich Felker <dalias@libc.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Link: http://lkml.kernel.org/r/1582520593-30704-4-git-send-email-anshuman.khandual@arm.com Signed-off-by:
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- 16 Mar, 2020 2 commits
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Dave Martin authored
An arch may want to tweak the mmap prot flags for an ELFexecutable's initial mappings. For example, arm64 is going to need to add PROT_BTI for executable pages in an ELF process whose executable is marked as using Branch Target Identification (an ARMv8.5-A control flow integrity feature). So that this can be done in a generic way, add a hook arch_elf_adjust_prot() to modify the prot flags as desired: arches can select CONFIG_HAVE_ELF_PROT and implement their own backend where necessary. By default, leave the prot flags unchanged. Signed-off-by:
Mark Brown <broonie@kernel.org> Signed-off-by:
Dave Martin <Dave.Martin@arm.com> Reviewed-by:
Catalin Marinas <catalin.marinas@arm.com> Reviewed-by:
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Dave Martin authored
ELF program properties will be needed for detecting whether to enable optional architecture or ABI features for a new ELF process. For now, there are no generic properties that we care about, so do nothing unless CONFIG_ARCH_USE_GNU_PROPERTY=y. Otherwise, the presence of properties using the PT_PROGRAM_PROPERTY phdrs entry (if any), and notify each property to the arch code. For now, the added code is not used. Signed-off-by:
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- 31 Jan, 2020 8 commits
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Alexey Dobriyan authored
Unmapping whole address space at once with munmap(0, (1ULL<<47) - 4096) or equivalent will create empty coredump. It is silly way to exit, however registers content may still be useful. The right to coredump is fundamental right of a process! Link: http://lkml.kernel.org/r/20191222150137.GA1277@avx2 Signed-off-by:
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Alexey Dobriyan authored
array_size() macro will do overflow check anyway. Link: http://lkml.kernel.org/r/20191222144009.GB24341@avx2 Signed-off-by:
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Alexey Dobriyan authored
Comment says ELF header is "too large to be on stack". 64 bytes on 64-bit is not large by any means. Link: http://lkml.kernel.org/r/20191222143850.GA24341@avx2 Signed-off-by:
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Alexey Dobriyan authored
If some mapping goes past TASK_SIZE it will be rejected by kernel which means no such userspace binaries exist. Mark every such check as unlikely. Link: http://lkml.kernel.org/r/20191215124355.GA21124@avx2 Signed-off-by:
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Alexey Dobriyan authored
"current->mm" pointer is stable in general except few cases one of which execve(2). Compiler can't treat is as stable but it _is_ stable most of the time. During ELF loading process ->mm becomes stable right after flush_old_exec(). Help compiler by caching current->mm, otherwise it continues to refetch it. add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-141 (-141) Function old new delta elf_core_dump 5062 5039 -23 load_elf_binary 5426 5308 -118 Note: other cases are left as is because it is either pessimisation or no change in binary size. Link: http://lkml.kernel.org/r/20191215124755.GB21124@avx2 Signed-off-by:
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Alexey Dobriyan authored
ELF header is read into bprm->buf[] by generic execve code. Save a memcpy and allocate just one header for the interpreter instead of two headers (64 bytes instead of 128 on 64-bit). Link: http://lkml.kernel.org/r/20191208171242.GA19716@avx2 Signed-off-by:
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Alexey Dobriyan authored
Only executable segments should be accounted to ->start_code just like they do to ->end_code (correctly). Link: http://lkml.kernel.org/r/20191208171410.GB19716@avx2 Signed-off-by:
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Alexey Dobriyan authored
Filling auxv vector as array with index (auxv[i++] = ...) generates terrible code. "saved_auxv" should be reworked because it is the worst member of mm_struct by size/usefullness ratio but do it later. Meanwhile help gcc a little with *auxv++ idiom. Space savings on x86_64: add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-127 (-127) Function old new delta load_elf_binary 5470 5343 -127 Link: http://lkml.kernel.org/r/20191208172301.GD19716@avx2 Signed-off-by:
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- 05 Dec, 2019 2 commits
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Alexey Dobriyan authored
ELF reads done by the kernel have very complicated error detection code which better live in one place. Link: http://lkml.kernel.org/r/20191005165215.GB26927@avx2 Signed-off-by:
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Alexey Dobriyan authored
Link: http://lkml.kernel.org/r/20191005165049.GA26927@avx2 Signed-off-by:
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- 15 Nov, 2019 1 commit
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Arnd Bergmann authored
We store elapsed time for a crashed process in struct elf_prstatus using 'timeval' structures. Once glibc starts using 64-bit time_t, this becomes incompatible with the kernel's idea of timeval since the structure layout no longer matches on 32-bit architectures. This changes the definition of the elf_prstatus structure to use __kernel_old_timeval instead, which is hardcoded to the currently used binary layout. There is no risk of overflow in y2038 though, because the time values are all relative times, and can store up to 68 years of process elapsed time. There is a risk of applications breaking at build time when they use the new kernel headers and expect the type to be exactly 'timeval' rather than a structure that has the same fields as before. Those applications have to be modified to deal with 64-bit time_t anyway. Signed-off-by:Arnd Bergmann <arnd@arndb.de>
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- 06 Oct, 2019 1 commit
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Linus Torvalds authored
In commit 4ed28639 ("fs, elf: drop MAP_FIXED usage from elf_map") we changed elf to use MAP_FIXED_NOREPLACE instead of MAP_FIXED for the executable mappings. Then, people reported that it broke some binaries that had overlapping segments from the same file, and commit ad55eac7 ("elf: enforce MAP_FIXED on overlaying elf segments") re-instated MAP_FIXED for some overlaying elf segment cases. But only some - despite the summary line of that commit, it only did it when it also does a temporary brk vma for one obvious overlapping case. Now Russell King reports another overlapping case with old 32-bit x86 binaries, which doesn't trigger that limited case. End result: we had better just drop MAP_FIXED_NOREPLACE entirely, and go back to MAP_FIXED. Yes, it's a sign of old binaries generated with old tool-chains, but we do pride ourselves on not breaking existing setups. This still leaves MAP_FIXED_NOREPLACE in place for the load_elf_interp() and the old load_elf_library() use-cases, because nobody has reported breakage for those. Yet. Note that in all the cases seen so far, the overlapping elf sections seem to be just re-mapping of the same executable with different section attributes. We could possibly introduce a new MAP_FIXED_NOFILECHANGE flag or similar, which acts like NOREPLACE, but allows just remapping the same executable file using different protection flags. It's not clear that would make a huge difference to anything, but if people really hate that "elf remaps over previous maps" behavior, maybe at least a more limited form of remapping would alleviate some concerns. Alternatively, we should take a look at our elf_map() logic to see if we end up not mapping things properly the first time. In the meantime, this is the minimal "don't do that then" patch while people hopefully think about it more. Reported-by:
Russell King <linux@armlinux.org.uk> Fixes: 4ed28639 ("fs, elf: drop MAP_FIXED usage from elf_map") Fixes: ad55eac7 ("elf: enforce MAP_FIXED on overlaying elf segments") Cc: Michal Hocko <mhocko@suse.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by:
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- 26 Sep, 2019 1 commit
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Kees Cook authored
When brk was moved for binaries without an interpreter, it should have been limited to ET_DYN only. In other words, the special case was an ET_DYN that lacks an INTERP, not just an executable that lacks INTERP. The bug manifested for giant static executables, where the brk would end up in the middle of the text area on 32-bit architectures. Reported-and-tested-by:
Richard Kojedzinszky <richard@kojedz.in> Fixes: bbdc6076 ("binfmt_elf: move brk out of mmap when doing direct loader exec") Cc: stable@vger.kernel.org Signed-off-by:
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- 24 Sep, 2019 1 commit
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Alexandre Ghiti authored
Patch series "Provide generic top-down mmap layout functions", v6. This series introduces generic functions to make top-down mmap layout easily accessible to architectures, in particular riscv which was the initial goal of this series. The generic implementation was taken from arm64 and used successively by arm, mips and finally riscv. Note that in addition the series fixes 2 issues: - stack randomization was taken into account even if not necessary. - [1] fixed an issue with mmap base which did not take into account randomization but did not report it to arm and mips, so by moving arm64 into a generic library, this problem is now fixed for both architectures. This work is an effort to factorize architecture functions to avoid code duplication and oversights as in [1]. [1]: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html This patch (of 14): This preparatory commit moves this function so that further introduction of generic topdown mmap layout is contained only in mm/util.c. Link: http://lkml.kernel.org/r/20190730055113.23635-2-alex@ghiti.fr Signed-off-by:
Alexandre Ghiti <alex@ghiti.fr> Acked-by:
Luis Chamberlain <mcgrof@kernel.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Burton <paul.burton@mips.com> Cc: James Hogan <jhogan@kernel.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by:
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- 17 Jul, 2019 1 commit
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Alexey Dobriyan authored
"passed_fileno" variable was deleted 11 years ago in 2.6.25. Link: http://lkml.kernel.org/r/20190529201747.GA23248@avx2 Fixes: d20894a2 ("Remove a.out interpreter support in ELF loader") Signed-off-by:
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- 21 May, 2019 1 commit
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Thomas Gleixner authored
Add SPDX license identifiers to all files which: - Have no license information of any form - Have MODULE_LICENCE("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>
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- 15 May, 2019 3 commits
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Kees Cook authored
Commmit eab09532 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE"), made changes in the rare case when the ELF loader was directly invoked (e.g to set a non-inheritable LD_LIBRARY_PATH, testing new versions of the loader), by moving into the mmap region to avoid both ET_EXEC and PIE binaries. This had the effect of also moving the brk region into mmap, which could lead to the stack and brk being arbitrarily close to each other. An unlucky process wouldn't get its requested stack size and stack allocations could end up scribbling on the heap. This is illustrated here. In the case of using the loader directly, brk (so helpfully identified as "[heap]") is allocated with the _loader_ not the binary. For example, with ASLR entirely disabled, you can see this more clearly: $ /bin/cat /proc/self/maps 555555554000-55555555c000 r-xp 00000000 ... /bin/cat 55555575b000-55555575c000 r--p 00007000 ... /bin/cat 55555575c000-55555575d000 rw-p 00008000 ... /bin/cat 55555575d000-55555577e000 rw-p 00000000 ... [heap] ... 7ffff7ff7000-7ffff7ffa000 r--p 00000000 ... [vvar] 7ffff7ffa000-7ffff7ffc000 r-xp 00000000 ... [vdso] 7ffff7ffc000-7ffff7ffd000 r--p 00027000 ... /lib/x86_64-linux-gnu/ld-2.27.so 7ffff7ffd000-7ffff7ffe000 rw-p 00028000 ... /lib/x86_64-linux-gnu/ld-2.27.so 7ffff7ffe000-7ffff7fff000 rw-p 00000000 ... 7ffffffde000-7ffffffff000 rw-p 00000000 ... [stack] $ /lib/x86_64-linux-gnu/ld-2.27.so /bin/cat /proc/self/maps ... 7ffff7bcc000-7ffff7bd4000 r-xp 00000000 ... /bin/cat 7ffff7bd4000-7ffff7dd3000 ---p 00008000 ... /bin/cat 7ffff7dd3000-7ffff7dd4000 r--p 00007000 ... /bin/cat 7ffff7dd4000-7ffff7dd5000 rw-p 00008000 ... /bin/cat 7ffff7dd5000-7ffff7dfc000 r-xp 00000000 ... /lib/x86_64-linux-gnu/ld-2.27.so 7ffff7fb2000-7ffff7fd6000 rw-p 00000000 ... 7ffff7ff7000-7ffff7ffa000 r--p 00000000 ... [vvar] 7ffff7ffa000-7ffff7ffc000 r-xp 00000000 ... [vdso] 7ffff7ffc000-7ffff7ffd000 r--p 00027000 ... /lib/x86_64-linux-gnu/ld-2.27.so 7ffff7ffd000-7ffff7ffe000 rw-p 00028000 ... /lib/x86_64-linux-gnu/ld-2.27.so 7ffff7ffe000-7ffff8020000 rw-p 00000000 ... [heap] 7ffffffde000-7ffffffff000 rw-p 00000000 ... [stack] The solution is to move brk out of mmap and into ELF_ET_DYN_BASE since nothing is there in the direct loader case (and ET_EXEC is still far away at 0x400000). Anything that ran before should still work (i.e. the ultimately-launched binary already had the brk very far from its text, so this should be no different from a COMPAT_BRK standpoint). The only risk I see here is that if someone started to suddenly depend on the entire memory space lower than the mmap region being available when launching binaries via a direct loader execs which seems highly unlikely, I'd hope: this would mean a binary would _not_ work when exec()ed normally. (Note that this is only done under CONFIG_ARCH_HAS_ELF_RANDOMIZATION when randomization is turned on.) Link: http://lkml.kernel.org/r/20190422225727.GA21011@beast Link: https://lkml.kernel.org/r/CAGXu5jJ5sj3emOT2QPxQkNQk0qbU6zEfu9=Omfhx_p0nCKPSjA@mail.gmail.com Fixes: eab09532 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE") Signed-off-by:
Ali Saidi <alisaidi@amazon.com> Cc: Ali Saidi <alisaidi@amazon.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jann Horn <jannh@google.com> Signed-off-by:
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Alexey Dobriyan authored
Get "current_pt_regs" pointer right before usage. Space savings on x86_64: add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-180 (-180) Function old new delta load_elf_binary 5806 5626 -180 !!! Looks like the compiler doesn't know that "current_pt_regs" is stable pointer (because it doesn't know ->stack isn't) even though it knows that "current" is stable pointer. So it saves it in the very beginning and then tries to carry it through a lot of code. Here is what happens here: load_elf_binary() ... mov rax,QWORD PTR gs:0x14c00 mov r13,QWORD PTR [rax+0x18] r13 = current->stack call kmem_cache_alloc # first kmalloc [980 bytes later!] # let's spill that sucker because we need a register # for "load_bias" calculations at # # if (interpreter) { # load_bias = ELF_ET_DYN_BASE; # if (current->flags & PF_RANDOMIZE) # load_bias += arch_mmap_rnd(); # elf_flags |= elf_fixed; # } mov QWORD PTR [rsp+0x68],r13 If this is not _the_ root cause it is still eeeeh. After the patch things become much simpler: mov rax, QWORD PTR gs:0x14c00 # current mov rdx, QWORD PTR [rax+0x18] # current->stack movq [rdx+0x3fb8], 0 # fill pt_regs ... call finalize_exec Link: http://lkml.kernel.org/r/20190419200343.GA19788@avx2 Signed-off-by: -
Alexey Dobriyan authored
There are two places where mapping protections are calculated: one for executable, another one for interpreter -- take them out. ELF read and execute permissions are interchanged with Linux PROT_READ and PROT_EXEC, microoptimizations are welcome! Link: http://lkml.kernel.org/r/20190417213413.GB26474@avx2 Signed-off-by:
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