[v6.1] general protection fault in proc_map_files_readdir

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13d706b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=d999409d5f3eeec9c1a6
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a9aa438e39c2/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a7b5afd2e170/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c7673d370fb/bzImage-dc5c83b7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d99940...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc000000002b: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000158-0x000000000000015f]
CPU: 0 PID: 11314 Comm: syz.4.2142 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__lock_acquire+0xf8/0x7c40 kernel/locking/lockdep.c:4933
Code: 42 0f b6 04 00 84 c0 0f 85 e9 64 00 00 83 3d 52 40 bd 0c 00 0f 84 80 27 00 00 83 3d 41 b9 3b 0b 00 74 2a 4c 89 e8 48 c1 e8 03 <42> 80 3c 00 00 74 12 4c 89 ef e8 39 61 6f 00 49 b8 00 00 00 00 00
RSP: 0018:ffffc90005b9f820 EFLAGS: 00010006
RAX: 000000000000002b RBX: 0000000000000000 RCX: 1ffff92000b73f24
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000158
RBP: ffffc90005b9fa50 R08: dffffc0000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1c4215e R12: 0000000000000001
R13: 0000000000000158 R14: 0000000000000000 R15: 0000000000000001
FS: 00007f589a10e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3031bff8 CR3: 000000004d342000 CR4: 00000000003506f0
Call Trace:
<TASK>
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
down_read_killable+0x4c/0x340 kernel/locking/rwsem.c:1543
mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
proc_map_files_readdir+0x3c1/0x970 fs/proc/base.c:2413
iterate_dir+0x213/0x550 fs/readdir.c:-1
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64+0xf2/0x270 fs/readdir.c:354
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: 0033:0x7f589919de99
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:00007f589a10e028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f5899425fa0 RCX: 00007f589919de99
RDX: 0000000000000034 RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007f5899233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5899426038 R14: 00007f5899425fa0 R15: 00007ffc019be548
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__lock_acquire+0xf8/0x7c40 kernel/locking/lockdep.c:4933
Code: 42 0f b6 04 00 84 c0 0f 85 e9 64 00 00 83 3d 52 40 bd 0c 00 0f 84 80 27 00 00 83 3d 41 b9 3b 0b 00 74 2a 4c 89 e8 48 c1 e8 03 <42> 80 3c 00 00 74 12 4c 89 ef e8 39 61 6f 00 49 b8 00 00 00 00 00
RSP: 0018:ffffc90005b9f820 EFLAGS: 00010006
RAX: 000000000000002b RBX: 0000000000000000 RCX: 1ffff92000b73f24
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000158
RBP: ffffc90005b9fa50 R08: dffffc0000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1c4215e R12: 0000000000000001
R13: 0000000000000158 R14: 0000000000000000 R15: 0000000000000001
FS: 00007f589a10e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3031bff8 CR3: 000000004d342000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
0: 42 0f b6 04 00 movzbl (%rax,%r8,1),%eax
5: 84 c0 test %al,%al
7: 0f 85 e9 64 00 00 jne 0x64f6
d: 83 3d 52 40 bd 0c 00 cmpl $0x0,0xcbd4052(%rip) # 0xcbd4066
14: 0f 84 80 27 00 00 je 0x279a
1a: 83 3d 41 b9 3b 0b 00 cmpl $0x0,0xb3bb941(%rip) # 0xb3bb962
21: 74 2a je 0x4d
23: 4c 89 e8 mov %r13,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 00 00 cmpb $0x0,(%rax,%r8,1) <-- trapping instruction
2f: 74 12 je 0x43
31: 4c 89 ef mov %r13,%rdi
34: e8 39 61 6f 00 call 0x6f6172
39: 49 rex.WB
3a: b8 00 00 00 00 mov $0x0,%eax


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