[moderation] [fs?] KASAN: null-ptr-deref Read in drop_buffers (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc77806cf3b4 Merge tag 'rust-fixes-6.18' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10bb2012580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b944b1e5afd39857
dashboard link: https://syzkaller.appspot.com/bug?extid=72b1b84482864c5f8dba
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
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/68fb23b44e5d/disk-dc77806c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dadcf706cdeb/vmlinux-dc77806c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/42d0ccc01f3f/bzImage-dc77806c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+72b1b8...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
BUG: KASAN: null-ptr-deref in buffer_busy fs/buffer.c:2886 [inline]
BUG: KASAN: null-ptr-deref in drop_buffers.constprop.0+0x89/0x340 fs/buffer.c:2898
Read of size 4 at addr 0000000000000060 by task kswapd0/84

CPU: 0 UID: 0 PID: 84 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
kasan_report+0xe0/0x110 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:194 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:200
instrument_atomic_read include/linux/instrumented.h:68 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
buffer_busy fs/buffer.c:2886 [inline]
drop_buffers.constprop.0+0x89/0x340 fs/buffer.c:2898
try_to_free_buffers+0x21c/0x2d0 fs/buffer.c:2952
filemap_release_folio+0x219/0x280 mm/filemap.c:4423
shrink_folio_list+0x28a5/0x4800 mm/vmscan.c:1519
evict_folios+0x79c/0x1b30 mm/vmscan.c:4745
try_to_shrink_lruvec+0x585/0x9b0 mm/vmscan.c:4908
shrink_one+0x3e3/0x7a0 mm/vmscan.c:4953
shrink_many mm/vmscan.c:5016 [inline]
lru_gen_shrink_node mm/vmscan.c:5094 [inline]
shrink_node+0x26cb/0x3d80 mm/vmscan.c:6081
kswapd_shrink_node mm/vmscan.c:6941 [inline]
balance_pgdat+0xbb8/0x1a50 mm/vmscan.c:7124
kswapd+0x590/0xb90 mm/vmscan.c:7389
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
==================================================================


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