kernel.git/fs/binfmt_elf.c, branch linux-6.10.y

ELF: fix kernel.randomize_va_space double read

2024-09-12T09:12:50Z

[ Upstream commit 2a97388a807b6ab5538aa8f8537b2463c6988bd2 ] ELF loader uses "randomize_va_space" twice. It is sysctl and can change at any moment, so 2 loads could see 2 different values in theory with unpredictable consequences. Issue exactly one load for consistent value across one exec. Signed-off-by: Alexey Dobriyan Link: https://lore.kernel.org/r/3329905c-7eb8-400a-8f0a-d87cff979b5b@p183 Signed-off-by: Kees Cook Signed-off-by: Sasha Levin

Merge tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-05-19T21:02:03Z

Pull non-mm updates from Andrew Morton: "Mainly singleton patches, documented in their respective changelogs. Notable series include: - Some maintenance and performance work for ocfs2 in Heming Zhao's series "improve write IO performance when fragmentation is high". - Some ocfs2 bugfixes from Su Yue in the series "ocfs2 bugs fixes exposed by fstests". - kfifo header rework from Andy Shevchenko in the series "kfifo: Clean up kfifo.h". - GDB script fixes from Florian Rommel in the series "scripts/gdb: Fixes for $lx_current and $lx_per_cpu". - After much discussion, a coding-style update from Barry Song explaining one reason why inline functions are preferred over macros. The series is "codingstyle: avoid unused parameters for a function-like macro"" * tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (62 commits) fs/proc: fix softlockup in __read_vmcore nilfs2: convert BUG_ON() in nilfs_finish_roll_forward() to WARN_ON() scripts: checkpatch: check unused parameters for function-like macro Documentation: coding-style: ask function-like macros to evaluate parameters nilfs2: use __field_struct() for a bitwise field selftests/kcmp: remove unused open mode nilfs2: remove calls to folio_set_error() and folio_clear_error() kernel/watchdog_perf.c: tidy up kerneldoc watchdog: allow nmi watchdog to use raw perf event watchdog: handle comma separated nmi_watchdog command line nilfs2: make superblock data array index computation sparse friendly squashfs: remove calls to set the folio error flag squashfs: convert squashfs_symlink_read_folio to use folio APIs scripts/gdb: fix detection of current CPU in KGDB scripts/gdb: make get_thread_info accept pointers scripts/gdb: fix parameter handling in $lx_per_cpu scripts/gdb: fix failing KGDB detection during probe kfifo: don't use "proxy" headers media: stih-cec: add missing io.h media: rc: add missing io.h ...

fs/coredump: Enable dynamic configuration of max file note size

2024-05-08T16:53:00Z

Introduce the capability to dynamically configure the maximum file note size for ELF core dumps via sysctl. Why is this being done? We have observed that during a crash when there are more than 65k mmaps in memory, the existing fixed limit on the size of the ELF notes section becomes a bottleneck. The notes section quickly reaches its capacity, leading to incomplete memory segment information in the resulting coredump. This truncation compromises the utility of the coredumps, as crucial information about the memory state at the time of the crash might be omitted. This enhancement removes the previous static limit of 4MB, allowing system administrators to adjust the size based on system-specific requirements or constraints. Eg: $ sysctl -a | grep core_file_note_size_limit kernel.core_file_note_size_limit = 4194304 $ sysctl -n kernel.core_file_note_size_limit 4194304 $echo 519304 > /proc/sys/kernel/core_file_note_size_limit $sysctl -n kernel.core_file_note_size_limit 519304 Attempting to write beyond the ceiling value of 16MB $echo 17194304 > /proc/sys/kernel/core_file_note_size_limit bash: echo: write error: Invalid argument Signed-off-by: Vijay Nag Signed-off-by: Allen Pais Link: https://lore.kernel.org/r/20240506193700.7884-1-apais@linux.microsoft.com Signed-off-by: Kees Cook

regset: use kvzalloc() for regset_get_alloc()

2024-04-26T04:07:03Z

While browsing through ChromeOS crash reports, I found one with an allocation failure that looked like this: chrome: page allocation failure: order:7, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=urgent,mems_allowed=0 CPU: 7 PID: 3295 Comm: chrome Not tainted 5.15.133-20574-g8044615ac35c #1 (HASH:1162 1) Hardware name: Google Lazor (rev3 - 8) with KB Backlight (DT) Call trace: ... warn_alloc+0x104/0x174 __alloc_pages+0x5f0/0x6e4 kmalloc_order+0x44/0x98 kmalloc_order_trace+0x34/0x124 __kmalloc+0x228/0x36c __regset_get+0x68/0xcc regset_get_alloc+0x1c/0x28 elf_core_dump+0x3d8/0xd8c do_coredump+0xeb8/0x1378 get_signal+0x14c/0x804 ... An order 7 allocation is (1 << 7) contiguous pages, or 512K. It's not a surprise that this allocation failed on a system that's been running for a while. More digging showed that it was fairly easy to see the order 7 allocation by just sending a SIGQUIT to chrome (or other processes) to generate a core dump. The actual amount being allocated was 279,584 bytes and it was for "core_note_type" NT_ARM_SVE. There was quite a bit of discussion [1] on the mailing lists in response to my v1 patch attempting to switch to vmalloc. The overall conclusion was that we could likely reduce the 279,584 byte allocation by quite a bit and Mark Brown has sent a patch to that effect [2]. However even with the 279,584 byte allocation gone there are still 65,552 byte allocations. These are just barely more than the 65,536 bytes and thus would require an order 5 allocation. An order 5 allocation is still something to avoid unless necessary and nothing needs the memory here to be contiguous. Change the allocation to kvzalloc() which should still be efficient for small allocations but doesn't force the memory subsystem to work hard (and maybe fail) at getting a large contiguous chunk. [1] https://lore.kernel.org/r/20240201171159.1.Id9ad163b60d21c9e56c2d686b0cc9083a8ba7924@changeid [2] https://lore.kernel.org/r/20240203-arm64-sve-ptrace-regset-size-v1-1-2c3ba1386b9e@kernel.org Link: https://lkml.kernel.org/r/20240205092626.v2.1.Id9ad163b60d21c9e56c2d686b0cc9083a8ba7924@changeid Signed-off-by: Douglas Anderson Reviewed-by: Catalin Marinas Cc: Al Viro Cc: Christian Brauner Cc: Dave Martin Cc: Eric Biederman Cc: Jan Kara Cc: Kees Cook Cc: Mark Brown Cc: Matthew Wilcox (Oracle) Cc: Oleg Nesterov Cc: Will Deacon Signed-off-by: Andrew Morton

binfmt_elf: Leave a gap between .bss and brk

2024-04-24T19:20:35Z

Currently the brk starts its randomization immediately after .bss, which means there is a chance that when the random offset is 0, linear overflows from .bss can reach into the brk area. Leave at least a single page gap between .bss and brk (when it has not already been explicitly relocated into the mmap range). Reported-by: Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Link: https://lore.kernel.org/r/20240217062545.1631668-2-keescook@chromium.org Signed-off-by: Kees Cook

binfmt_elf: Only report padzero() errors when PROT_WRITE

2023-10-04T02:48:44Z

Errors with padzero() should be caught unless we're expecting a pathological (non-writable) segment. Report -EFAULT only when PROT_WRITE is present. Additionally add some more documentation to padzero(), elf_map(), and elf_load(). Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Tested-by: Pedro Falcato Signed-off-by: Sebastian Ott Link: https://lore.kernel.org/r/20230929032435.2391507-5-keescook@chromium.org Signed-off-by: Kees Cook

binfmt_elf: Use elf_load() for library

2023-10-04T02:48:43Z

While load_elf_library() is a libc5-ism, we can still replace most of its contents with elf_load() as well, further simplifying the code. Some historical context: - libc4 was a.out and used uselib (a.out support has been removed) - libc5 was ELF and used uselib (there may still be users) - libc6 is ELF and has never used uselib Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Tested-by: Pedro Falcato Signed-off-by: Sebastian Ott Link: https://lore.kernel.org/r/20230929032435.2391507-4-keescook@chromium.org Signed-off-by: Kees Cook

binfmt_elf: Use elf_load() for interpreter

2023-09-29T16:54:27Z

Handle arbitrary memsz>filesz in interpreter ELF segments, instead of only supporting it in the last segment (which is expected to be the BSS). Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Reported-by: Pedro Falcato Closes: https://lore.kernel.org/lkml/20221106021657.1145519-1-pedro.falcato@gmail.com/ Tested-by: Pedro Falcato Signed-off-by: Sebastian Ott Link: https://lore.kernel.org/r/20230929032435.2391507-3-keescook@chromium.org Signed-off-by: Kees Cook

binfmt_elf: elf_bss no longer used by load_elf_binary()

2023-09-29T16:54:27Z

With the BSS handled generically via the new filesz/memsz mismatch handling logic in elf_load(), elf_bss no longer needs to be tracked. Drop the variable. Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Tested-by: Pedro Falcato Signed-off-by: Sebastian Ott Link: https://lore.kernel.org/r/20230929032435.2391507-2-keescook@chromium.org Signed-off-by: Kees Cook

binfmt_elf: Support segments with 0 filesz and misaligned starts

2023-09-29T16:54:27Z

Implement a helper elf_load() that wraps elf_map() and performs all of the necessary work to ensure that when "memsz > filesz" the bytes described by "memsz > filesz" are zeroed. An outstanding issue is if the first segment has filesz 0, and has a randomized location. But that is the same as today. In this change I replaced an open coded padzero() that did not clear all of the way to the end of the page, with padzero() that does. I also stopped checking the return of padzero() as there is at least one known case where testing for failure is the wrong thing to do. It looks like binfmt_elf_fdpic may have the proper set of tests for when error handling can be safely completed. I found a couple of commits in the old history https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git, that look very interesting in understanding this code. commit 39b56d902bf3 ("[PATCH] binfmt_elf: clearing bss may fail") commit c6e2227e4a3e ("[SPARC64]: Missing user access return value checks in fs/binfmt_elf.c and fs/compat.c") commit 5bf3be033f50 ("v2.4.10.1 -> v2.4.10.2") Looking at commit 39b56d902bf3 ("[PATCH] binfmt_elf: clearing bss may fail"): > commit 39b56d902bf35241e7cba6cc30b828ed937175ad > Author: Pavel Machek > Date: Wed Feb 9 22:40:30 2005 -0800 > > [PATCH] binfmt_elf: clearing bss may fail > > So we discover that Borland's Kylix application builder emits weird elf > files which describe a non-writeable bss segment. > > So remove the clear_user() check at the place where we zero out the bss. I > don't _think_ there are any security implications here (plus we've never > checked that clear_user() return value, so whoops if it is a problem). > > Signed-off-by: Pavel Machek > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds It seems pretty clear that binfmt_elf_fdpic with skipping clear_user() for non-writable segments and otherwise calling clear_user(), aka padzero(), and checking it's return code is the right thing to do. I just skipped the error checking as that avoids breaking things. And notably, it looks like Borland's Kylix died in 2005 so it might be safe to just consider read-only segments with memsz > filesz an error. Reported-by: Sebastian Ott Reported-by: Thomas Weißschuh Closes: https://lkml.kernel.org/r/20230914-bss-alloc-v1-1-78de67d2c6dd@weissschuh.net Signed-off-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/87sf71f123.fsf@email.froward.int.ebiederm.org Tested-by: Pedro Falcato Signed-off-by: Sebastian Ott Link: https://lore.kernel.org/r/20230929032435.2391507-1-keescook@chromium.org Signed-off-by: Kees Cook