syzbot
general protection fault in drop_buffers
Status:
upstream: reported on 2026/10/30 18:43
Reported-by: syzbot+27f5635fb0e922751b7f@syzkaller.appspotmail.com
First crash: 5d21h, last: 5d21h
Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 0 PID: 29023 Comm: syz.8.9158 Tainted: G S B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:29 [inline]
RIP: 0010:atomic_read include/linux/atomic/atomic-instrumented.h:28 [inline]
RIP: 0010:buffer_busy fs/buffer.c:2784 [inline]
RIP: 0010:drop_buffers+0x76/0x6d0 fs/buffer.c:2796
Code: 20 4c 8b 3b 4d 89 fc 4d 8d 74 24 60 4c 89 f7 be 04 00 00 00 e8 bb 64 e1 ff 4c 89 f0 48 c1 e8 03 48 bb 00 00 00 00 00 fc ff df <0f> b6 04 18 84 c0 75 60 41 8b 6c 24 60 4c 89 e0 48 c1 e8 03 80 3c
RSP: 0018:ffffc900044e69d8 EFLAGS: 00010206
RAX: 000000000000000c RBX: dffffc0000000000 RCX: ffffffff81f26945
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000060
RBP: 0000000000000000 R08: 0000000000000000 R09: 1ffff1100e60d961
R10: dffffc0000000000 R11: ffffed100e60d962 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000060 R15: ffff88807306caa8
FS: 00007f98be0486c0(0000) GS:ffff8880b8c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f37e3d5da08 CR3: 000000007a166000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
try_to_free_buffers+0x22c/0x580 fs/buffer.c:2830
shrink_folio_list+0x22e1/0x8050 mm/vmscan.c:2003
evict_folios+0x4e6b/0x70c0 mm/vmscan.c:5047
lru_gen_shrink_lruvec mm/vmscan.c:5228 [inline]
shrink_lruvec+0xb88/0x3f80 mm/vmscan.c:5923
shrink_node_memcgs mm/vmscan.c:6144 [inline]
shrink_node+0x68b/0x2890 mm/vmscan.c:6175
shrink_zones mm/vmscan.c:6416 [inline]
do_try_to_free_pages+0x650/0x1980 mm/vmscan.c:6478
try_to_free_mem_cgroup_pages+0x335/0x8c0 mm/vmscan.c:6793
mem_cgroup_resize_max+0x31d/0x430 mm/memcontrol.c:3506
mem_cgroup_write+0x1ff/0x220 mm/memcontrol.c:-1
cgroup_file_write+0x2c9/0x6a0 kernel/cgroup/cgroup.c:4130
kernfs_fop_write_iter+0x3a0/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2271 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x482/0x9a0 fs/read_write.c:584
ksys_write+0x14d/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f98bd19f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f98be048028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f98bd425fa0 RCX: 00007f98bd19f559
RDX: 000000000000001e RSI: 00002000000003c0 RDI: 0000000000000003
RBP: 00007f98bd236b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f98bd426038 R14: 00007f98bd425fa0 R15: 00007ffcb9cc6768
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:29 [inline]
RIP: 0010:atomic_read include/linux/atomic/atomic-instrumented.h:28 [inline]
RIP: 0010:buffer_busy fs/buffer.c:2784 [inline]
RIP: 0010:drop_buffers+0x76/0x6d0 fs/buffer.c:2796
Code: 20 4c 8b 3b 4d 89 fc 4d 8d 74 24 60 4c 89 f7 be 04 00 00 00 e8 bb 64 e1 ff 4c 89 f0 48 c1 e8 03 48 bb 00 00 00 00 00 fc ff df <0f> b6 04 18 84 c0 75 60 41 8b 6c 24 60 4c 89 e0 48 c1 e8 03 80 3c
RSP: 0018:ffffc900044e69d8 EFLAGS: 00010206
RAX: 000000000000000c RBX: dffffc0000000000 RCX: ffffffff81f26945
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000060
RBP: 0000000000000000 R08: 0000000000000000 R09: 1ffff1100e60d961
R10: dffffc0000000000 R11: ffffed100e60d962 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000060 R15: ffff88807306caa8
FS: 00007f98be0486c0(0000) GS:ffff8880b8c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3431bff8 CR3: 000000007a166000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 20 4c 8b 3b and %cl,0x3b(%rbx,%rcx,4)
4: 4d 89 fc mov %r15,%r12
7: 4d 8d 74 24 60 lea 0x60(%r12),%r14
c: 4c 89 f7 mov %r14,%rdi
f: be 04 00 00 00 mov $0x4,%esi
14: e8 bb 64 e1 ff call 0xffe164d4
19: 4c 89 f0 mov %r14,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 bb 00 00 00 00 00 movabs $0xdffffc0000000000,%rbx
27: fc ff df
* 2a: 0f b6 04 18 movzbl (%rax,%rbx,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 75 60 jne 0x92
32: 41 8b 6c 24 60 mov 0x60(%r12),%ebp
37: 4c 89 e0 mov %r12,%rax
3a: 48 c1 e8 03 shr $0x3,%rax
3e: 80 .byte 0x80
3f: 3c .byte 0x3c
Struck through repros no longer work on HEAD.