[moderation] [ext4?] KCSAN: data-race in do_sync_mmap_readahead / do_sync_mmap_readahead (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5bc1018675ec Merge tag 'pci-v6.15-fixes-3' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16121270580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fc7049672597c030
dashboard link: https://syzkaller.appspot.com/bug?extid=c0029a42ecaf45327127
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [adilger...@dilger.ca 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/b07ed9969a13/disk-5bc10186.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3abab03798d3/vmlinux-5bc10186.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8fca26b1845c/bzImage-5bc10186.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c0029a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_sync_mmap_readahead / do_sync_mmap_readahead

write to 0xffff88811743ced0 of 8 bytes by task 3645 on cpu 0:
do_sync_mmap_readahead+0x204/0x280 mm/filemap.c:3258
filemap_fault+0x311/0xb40 mm/filemap.c:3403
__do_fault+0xb9/0x200 mm/memory.c:5098
do_read_fault mm/memory.c:5518 [inline]
do_fault mm/memory.c:5652 [inline]
do_pte_missing mm/memory.c:4160 [inline]
handle_pte_fault mm/memory.c:5997 [inline]
__handle_mm_fault mm/memory.c:6140 [inline]
handle_mm_fault+0x110c/0x2ae0 mm/memory.c:6309
do_user_addr_fault+0x3fe/0x1090 arch/x86/mm/fault.c:1388
handle_page_fault arch/x86/mm/fault.c:1480 [inline]
exc_page_fault+0x54/0xc0 arch/x86/mm/fault.c:1538
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
fault_in_readable+0xfe/0x1b0 mm/gup.c:-1
fault_in_iov_iter_readable+0x129/0x210 lib/iov_iter.c:94
generic_perform_write+0x3cf/0x490 mm/filemap.c:4152
ext4_buffered_write_iter+0x1ee/0x3c0 fs/ext4/file.c:299
ext4_file_write_iter+0x383/0xf00 fs/ext4/file.c:-1
new_sync_write fs/read_write.c:591 [inline]
vfs_write+0x49d/0x8d0 fs/read_write.c:684
ksys_pwrite64 fs/read_write.c:791 [inline]
__do_sys_pwrite64 fs/read_write.c:799 [inline]
__se_sys_pwrite64 fs/read_write.c:796 [inline]
__x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:796
x64_sys_call+0xe45/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:19
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff88811743ced0 of 8 bytes by task 3663 on cpu 1:
do_sync_mmap_readahead+0x204/0x280 mm/filemap.c:3258
filemap_fault+0x311/0xb40 mm/filemap.c:3403
__do_fault+0xb9/0x200 mm/memory.c:5098
do_read_fault mm/memory.c:5518 [inline]
do_fault mm/memory.c:5652 [inline]
do_pte_missing mm/memory.c:4160 [inline]
handle_pte_fault mm/memory.c:5997 [inline]
__handle_mm_fault mm/memory.c:6140 [inline]
handle_mm_fault+0x110c/0x2ae0 mm/memory.c:6309
faultin_page mm/gup.c:1193 [inline]
__get_user_pages+0xde2/0x1d20 mm/gup.c:1491
populate_vma_page_range mm/gup.c:1929 [inline]
__mm_populate+0x243/0x3a0 mm/gup.c:2032
mm_populate include/linux/mm.h:3487 [inline]
vm_mmap_pgoff+0x232/0x2e0 mm/util.c:584
ksys_mmap_pgoff+0x268/0x310 mm/mmap.c:607
x64_sys_call+0x1602/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:10
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000032020bd -> 0x00000000032020be

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3663 Comm: syz.0.56 Not tainted 6.15.0-rc3-syzkaller-00342-g5bc1018675ec #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
EXT4-fs warning (device loop0): ext4_block_to_path:107: block 209748036 > max in inode 15
EXT4-fs warning (device loop0): ext4_block_to_path:107: block 209748040 > max in inode 15
EXT4-fs warning (device loop0): ext4_block_to_path:107: block 209748044 > max in inode 15
EXT4-fs warning (device loop0): ext4_block_to_path:107: block 209748048 > max in inode 15


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[syzbot]

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