[moderation] [mm?] KCSAN: data-race in shmem_file_splice_read / shmem_setattr (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5c24e4e9e708 Merge tag 'hid-for-linus-2024020101' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1385848fe80000
kernel config: https://syzkaller.appspot.com/x/.config?x=4aab723d3dfffc44
dashboard link: https://syzkaller.appspot.com/bug?extid=173277c2cd37ddaad093
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/939a791831ca/disk-5c24e4e9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ffa996f3841/vmlinux-5c24e4e9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/00a87458e25f/bzImage-5c24e4e9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+173277...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in shmem_file_splice_read / shmem_setattr

write to 0xffff888131089b40 of 8 bytes by task 7406 on cpu 1:
i_size_write include/linux/fs.h:932 [inline]
shmem_setattr+0x6fb/0x830 mm/shmem.c:1186
notify_change+0x866/0x8e0 fs/attr.c:499
do_truncate+0x116/0x150 fs/open.c:66
do_sys_ftruncate+0x2ba/0x3b0 fs/open.c:194
__do_sys_ftruncate fs/open.c:205 [inline]
__se_sys_ftruncate fs/open.c:203 [inline]
__x64_sys_ftruncate+0x33/0x40 fs/open.c:203
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888131089b40 of 8 bytes by task 7404 on cpu 0:
i_size_read include/linux/fs.h:910 [inline]
shmem_file_splice_read+0x145/0x600 mm/shmem.c:2961
do_splice_read fs/splice.c:985 [inline]
splice_direct_to_actor+0x268/0x660 fs/splice.c:1089
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3b9/0x960 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1356 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000000003dc -> 0x000000000000000d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7404 Comm: syz-executor.2 Not tainted 6.8.0-rc2-syzkaller-00084-g5c24e4e9e708 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.