[moderation] [mm?] KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 661e504db04c Merge tag 'for-6.10-rc6-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d2ebbe980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b9537cd00be479e
dashboard link: https://syzkaller.appspot.com/bug?extid=001e0f4dc8703945a00f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ee639c18925a/disk-661e504d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3729de99fbc0/vmlinux-661e504d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3a0202c4dcdb/bzImage-661e504d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+001e0f...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in shmem_add_to_page_cache / shmem_getattr

read-write to 0xffff888113245cc0 of 8 bytes by task 11271 on cpu 1:
shmem_add_to_page_cache+0x3b9/0x4b0 mm/shmem.c:797
shmem_alloc_and_add_folio mm/shmem.c:1689 [inline]
shmem_get_folio_gfp+0x500/0xb70 mm/shmem.c:2055
shmem_get_folio mm/shmem.c:2160 [inline]
shmem_write_begin+0xa0/0x1c0 mm/shmem.c:2743
generic_perform_write+0x1d5/0x410 mm/filemap.c:4015
shmem_file_write_iter+0xc8/0xf0 mm/shmem.c:2919
__kernel_write_iter+0x24f/0x4e0 fs/read_write.c:523
dump_emit_page fs/coredump.c:893 [inline]
dump_user_range+0x3a7/0x550 fs/coredump.c:954
elf_core_dump+0x1aeb/0x1c30 fs/binfmt_elf.c:2083
do_coredump+0xff6/0x1860 fs/coredump.c:767
get_signal+0xdc1/0x1080 kernel/signal.c:2894
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
irqentry_exit_to_user_mode+0x94/0x130 kernel/entry/common.c:231
irqentry_exit+0x12/0x50 kernel/entry/common.c:334
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffff888113245cc0 of 8 bytes by task 3079 on cpu 0:
shmem_getattr+0x69/0x200 mm/shmem.c:1127
vfs_getattr_nosec fs/stat.c:135 [inline]
vfs_getattr+0x19b/0x1e0 fs/stat.c:176
vfs_statx+0x140/0x320 fs/stat.c:248
vfs_fstatat+0xcd/0x100 fs/stat.c:304
__do_sys_newfstatat fs/stat.c:468 [inline]
__se_sys_newfstatat+0x58/0x260 fs/stat.c:462
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:462
x64_sys_call+0x1451/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000002ed -> 0x00000000000002f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3079 Comm: syz-executor Not tainted 6.10.0-rc6-syzkaller-00163-g661e504db04c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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