[moderation] [fs?] KCSAN: data-race in filemap_read_folio / filemap_read_folio (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5cd64d4f9268 Merge tag 'ceph-for-6.17-rc6' of https://gith..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d93934580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=a8c6d01205f921cf31bb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/de5f04f0aaee/disk-5cd64d4f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/969e9880ed32/vmlinux-5cd64d4f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7e3ded685661/bzImage-5cd64d4f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a8c6d0...@syzkaller.appspotmail.com

syz.6.1659: attempt to access beyond end of device
loop6: rw=0, sector=2065, nr_sectors = 1 limit=128
Buffer I/O error on dev loop6, logical block 2065, async page read
Buffer I/O error on dev loop6, logical block 2066, async page read
==================================================================
BUG: KCSAN: data-race in filemap_read_folio / filemap_read_folio

read-write to 0xffff88810f4b29a0 of 4 bytes by task 11233 on cpu 1:
shrink_readahead_size_eio mm/filemap.c:2355 [inline]
filemap_read_folio+0xea/0x110 mm/filemap.c:2425
filemap_fault+0x56a/0xb40 mm/filemap.c:3537
__do_fault+0xb9/0x200 mm/memory.c:5152
do_read_fault mm/memory.c:5573 [inline]
do_fault mm/memory.c:5707 [inline]
do_pte_missing mm/memory.c:4234 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0xf78/0x2c20 mm/memory.c:6364
do_user_addr_fault+0x793/0x1090 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
fault_in_readable+0xad/0x170 mm/gup.c:-1
fault_in_iov_iter_readable+0x129/0x210 lib/iov_iter.c:94
generic_perform_write+0x3cf/0x490 mm/filemap.c:4224
__generic_file_write_iter+0xec/0x120 mm/filemap.c:4289
generic_file_write_iter+0x8d/0x2f0 mm/filemap.c:4318
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x52a/0x960 fs/read_write.c:686
ksys_write+0xda/0x1a0 fs/read_write.c:738
__do_sys_write fs/read_write.c:749 [inline]
__se_sys_write fs/read_write.c:746 [inline]
__x64_sys_write+0x40/0x50 fs/read_write.c:746
x64_sys_call+0x27fe/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read-write to 0xffff88810f4b29a0 of 4 bytes by task 11227 on cpu 0:
shrink_readahead_size_eio mm/filemap.c:2355 [inline]
filemap_read_folio+0xea/0x110 mm/filemap.c:2425
filemap_fault+0x56a/0xb40 mm/filemap.c:3537
__do_fault+0xb9/0x200 mm/memory.c:5152
do_read_fault mm/memory.c:5573 [inline]
do_fault mm/memory.c:5707 [inline]
do_pte_missing mm/memory.c:4234 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0xf78/0x2c20 mm/memory.c:6364
faultin_page mm/gup.c:1144 [inline]
__get_user_pages+0x102e/0x1fa0 mm/gup.c:1446
populate_vma_page_range mm/gup.c:1880 [inline]
__mm_populate+0x243/0x3a0 mm/gup.c:1983
mm_populate include/linux/mm.h:3367 [inline]
vm_mmap_pgoff+0x232/0x2e0 mm/util.c:585
ksys_mmap_pgoff+0x268/0x310 mm/mmap.c:604
x64_sys_call+0x14a3/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:10
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000002 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11227 Comm: syz.6.1659 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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