[moderation] [mm?] KCSAN: data-race in shmem_file_read_iter / shmem_setattr (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 87adedeba51a Merge tag 'net-6.8-rc7' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12cd9716180000
kernel config: https://syzkaller.appspot.com/x/.config?x=53006d590acdf777
dashboard link: https://syzkaller.appspot.com/bug?extid=5ea14eed4d29c47f0456
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/85879d80665b/disk-87adedeb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/594eb01e8ed8/vmlinux-87adedeb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c4cbd4a49e35/bzImage-87adedeb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5ea14e...@syzkaller.appspotmail.com

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

write to 0xffff888139dd5e30 of 8 bytes by task 7621 on cpu 0:
i_size_write include/linux/fs.h:934 [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 0xffff888139dd5e30 of 8 bytes by task 7627 on cpu 1:
i_size_read include/linux/fs.h:912 [inline]
shmem_file_read_iter+0x96/0x550 mm/shmem.c:2777
call_read_iter include/linux/fs.h:2081 [inline]
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x5ab/0x6a0 fs/read_write.c:476
ksys_read+0xeb/0x1a0 fs/read_write.c:619
__do_sys_read fs/read_write.c:629 [inline]
__se_sys_read fs/read_write.c:627 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:627
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: 0x0000000000000000 -> 0x0000000002007fff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7627 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00120-g87adedeba51a #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.