syzbot
general protection fault in vsscanf
Status:
upstream: reported C repro on 2026/08/19 08:56
Reported-by: syzbot+76a2c4fd2ef62437fd6f@syzkaller.appspotmail.com
First crash: 20h52m, last: 19h18m
Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 5938 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:vsscanf+0x19a/0x2520 lib/vsprintf.c:3464
Code: 48 c7 c6 d0 6d 74 8e e8 64 72 07 f7 41 83 fe 25 74 4d 45 85 f6 0f 84 1e 22 00 00 48 ff c3 48 89 5c 24 78 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 bd 1b 00 00 41 0f b6 1f 45 0f b6 f6 44
RSP: 0018:ffffc90003387640 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff8ad68661 RCX: 0000000000000001
RDX: ffffffff8a80047c RSI: ffffffff8e746dd0 RDI: 0000000000000030
RBP: ffffc90003387770 R08: ffff888079948000 R09: 0000000000000002
R10: 0000000000000025 R11: 0000000000000000 R12: ffffffff8ad68660
R13: dffffc0000000000 R14: 0000000000000030 R15: 0000000000000000
FS: 000055557f0e7500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055acafcbba80 CR3: 0000000076a8b000 CR4: 00000000003506e0
Call Trace:
<TASK>
sscanf+0xe3/0x140 lib/vsprintf.c:3722
split_huge_pages_write+0x391/0x1b60 mm/huge_memory.c:3179
full_proxy_write+0x110/0x1c0 fs/debugfs/file.c:244
vfs_write+0x299/0x9a0 fs/read_write.c:582
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f328db9e0d9
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:00007fffb2c36c08 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f328de25fa0 RCX: 00007f328db9e0d9
RDX: 0000000000000005 RSI: 0000200000000600 RDI: 0000000000000003
RBP: 00007f328dc35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f328de25fac R14: 00007f328de25fa0 R15: 00007f328de25fa0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vsscanf+0x19a/0x2520 lib/vsprintf.c:3464
Code: 48 c7 c6 d0 6d 74 8e e8 64 72 07 f7 41 83 fe 25 74 4d 45 85 f6 0f 84 1e 22 00 00 48 ff c3 48 89 5c 24 78 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 bd 1b 00 00 41 0f b6 1f 45 0f b6 f6 44
RSP: 0018:ffffc90003387640 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff8ad68661 RCX: 0000000000000001
RDX: ffffffff8a80047c RSI: ffffffff8e746dd0 RDI: 0000000000000030
RBP: ffffc90003387770 R08: ffff888079948000 R09: 0000000000000002
R10: 0000000000000025 R11: 0000000000000000 R12: ffffffff8ad68660
R13: dffffc0000000000 R14: 0000000000000030 R15: 0000000000000000
FS: 000055557f0e7500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055acafcbba80 CR3: 0000000076a8b000 CR4: 00000000003506e0
----------------
Code disassembly (best guess):
0: 48 c7 c6 d0 6d 74 8e mov $0xffffffff8e746dd0,%rsi
7: e8 64 72 07 f7 call 0xf7077270
c: 41 83 fe 25 cmp $0x25,%r14d
10: 74 4d je 0x5f
12: 45 85 f6 test %r14d,%r14d
15: 0f 84 1e 22 00 00 je 0x2239
1b: 48 ff c3 inc %rbx
1e: 48 89 5c 24 78 mov %rbx,0x78(%rsp)
23: 4c 89 f8 mov %r15,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 bd 1b 00 00 jne 0x1bf4
37: 41 0f b6 1f movzbl (%r15),%ebx
3b: 45 0f b6 f6 movzbl %r14b,%r14d
3f: 44 rex.R
Struck through repros no longer work on HEAD.