[moderation] [ext4?] KCSAN: data-race in __filemap_add_folio / sync_bdevs (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc59e4fea9d8 Linux 7.2-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1247b3de580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=a942eb537f5c29968ff7
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [ja...@suse.com linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c30fa6298c88/disk-dc59e4fe.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d723159b1484/vmlinux-dc59e4fe.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c0487b8aa33d/bzImage-dc59e4fe.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a942eb...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __filemap_add_folio / sync_bdevs

read-write to 0xffff8881005f7178 of 8 bytes by task 2946 on cpu 0:
__filemap_add_folio+0x66e/0x880 mm/filemap.c:919
filemap_add_folio+0x1d3/0x350 mm/filemap.c:966
__filemap_get_folio_mpol+0x32e/0x840 mm/filemap.c:2022
__filemap_get_folio include/linux/pagemap.h:761 [inline]
grow_dev_folio fs/buffer.c:960 [inline]
grow_buffers fs/buffer.c:1026 [inline]
__getblk_slow fs/buffer.c:1044 [inline]
bdev_getblk+0x170/0x3c0 fs/buffer.c:1439
__getblk include/linux/buffer_head.h:382 [inline]
jbd2_journal_get_descriptor_buffer+0xce/0x210 fs/jbd2/journal.c:974
jbd2_journal_commit_transaction+0xc41/0x3260 fs/jbd2/commit.c:636
kjournald2+0x211/0x3d0 fs/jbd2/journal.c:199
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881005f7178 of 8 bytes by task 14789 on cpu 1:
sync_bdevs+0xd3/0x260 block/bdev.c:1278
ksys_sync fs/sync.c:105 [inline]
__ia32_sys_sync+0x81/0xb0 fs/sync.c:111
x64_sys_call+0x2f3a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:163
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000523 -> 0x0000000000000524

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 14789 Comm: syz.9.10116 Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


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