[moderation] [exfat?] KCSAN: data-race in fat_bmap / generic_write_end (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9bacdd8996c7 Merge tag 'for-6.7-rc1-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15673388e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=a91f789b98394377
dashboard link: https://syzkaller.appspot.com/bug?extid=65464efd1087dc110d9d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [hiro...@mail.parknet.co.jp linki...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org sj155...@samsung.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/be70757ec048/disk-9bacdd89.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/45e8c725b4dc/vmlinux-9bacdd89.xz
kernel image: https://storage.googleapis.com/syzbot-assets/82e551f976a9/bzImage-9bacdd89.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65464e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fat_bmap / generic_write_end

write to 0xffff888145015928 of 8 bytes by task 26019 on cpu 1:
i_size_write include/linux/fs.h:932 [inline]
generic_write_end+0x94/0x230 fs/buffer.c:2291
fat_write_end+0x4e/0x160 fs/fat/inode.c:244
generic_perform_write+0x267/0x410 mm/filemap.c:3929
__generic_file_write_iter+0xec/0x120 mm/filemap.c:4010
generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4039
do_iter_write+0x4ad/0x770 fs/read_write.c:860
vfs_iter_write+0x56/0x70 fs/read_write.c:901
iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888145015928 of 8 bytes by task 25999 on cpu 0:
i_size_read include/linux/fs.h:910 [inline]
is_exceed_eof fs/fat/cache.c:340 [inline]
fat_bmap+0x1d2/0x290 fs/fat/cache.c:375
__fat_get_block fs/fat/inode.c:129 [inline]
fat_get_block+0xd1/0x5e0 fs/fat/inode.c:190
block_read_full_folio+0x27a/0x710 fs/buffer.c:2399
do_mpage_readpage+0xc38/0xd80 fs/mpage.c:324
mpage_read_folio+0x5b/0xd0 fs/mpage.c:399
fat_read_folio+0x1c/0x20 fs/fat/inode.c:205
filemap_read_folio mm/filemap.c:2323 [inline]
filemap_update_page mm/filemap.c:2407 [inline]
filemap_get_pages+0xcfd/0xf90 mm/filemap.c:2521
filemap_splice_read+0x238/0x7f0 mm/filemap.c:2860
vfs_splice_read fs/splice.c:993 [inline]
splice_direct_to_actor+0x28c/0x690 fs/splice.c:1069
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1316 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000001000 -> 0x0000000000001126

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25999 Comm: syz-executor.0 Tainted: G W 6.7.0-rc1-syzkaller-00012-g9bacdd8996c7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
==================================================================


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[syzbot]

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