[syzbot] [io-uring?] general protection fault in io_uring_show_fdinfo

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 99d99825fc07 Merge tag 'nfs-for-6.6-1' of git://git.linux-..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12e9fc13a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=cce54b04d9a3d05b
dashboard link: https://syzkaller.appspot.com/bug?extid=216e2ea6e0bf4a0acdd7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1749fa10680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10211c10680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dc52c367d995/disk-99d99825.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4387aed6fe34/vmlinux-99d99825.xz
kernel image: https://storage.googleapis.com/syzbot-assets/653ab6d1ead8/bzImage-99d99825.xz

The issue was bisected to:

commit 2af89abda7d9c2aeb573677e2c498ddb09f8058a
Author: Pavel Begunkov <asml.s...@gmail.com>
Date: Thu Aug 24 22:53:32 2023 +0000

io_uring: add option to remove SQ indirection

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1017518fa80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1217518fa80000
console output: https://syzkaller.appspot.com/x/log.txt?x=1417518fa80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+216e2e...@syzkaller.appspotmail.com
Fixes: 2af89abda7d9 ("io_uring: add option to remove SQ indirection")

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 5026 Comm: syz-executor249 Not tainted 6.5.0-syzkaller-09276-g99d99825fc07 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
RIP: 0010:io_uring_show_fdinfo+0x391/0x1790 io_uring/fdinfo.c:96
Code: 00 00 00 42 80 3c 28 00 74 0f 48 8b 7c 24 30 e8 d5 9d 22 f7 48 8b 4c 24 30 44 21 f3 48 c1 e3 02 48 03 19 48 89 d8 48 c1 e8 03 <42> 8a 04 28 84 c0 0f 85 64 02 00 00 8b 1b 89 df 44 89 f6 e8 c7 c9
RSP: 0018:ffffc900038ffc20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8880299e60d0
RDX: ffff8880262f9dc0 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900038ffd98 R08: ffffffff8ac4995f R09: 1ffff11004f01013
R10: dffffc0000000000 R11: ffffed1004f01014 R12: ffff888021153de0
R13: dffffc0000000000 R14: 0000000000003fff R15: 0000000000000001
FS: 000055555700b480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6f2394f653 CR3: 0000000029588000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
seq_show+0x57d/0x6a0 fs/proc/fd.c:70
traverse+0x1d5/0x530 fs/seq_file.c:111
seq_lseek+0x129/0x240 fs/seq_file.c:323
vfs_llseek fs/read_write.c:289 [inline]
ksys_lseek fs/read_write.c:302 [inline]
__do_sys_lseek fs/read_write.c:313 [inline]
__se_sys_lseek fs/read_write.c:311 [inline]
__x64_sys_lseek+0x14f/0x1d0 fs/read_write.c:311
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f6f238f2fe9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc7fc29dc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 00007ffc7fc29de0 RCX: 00007f6f238f2fe9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc7fc2a048 R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:io_uring_show_fdinfo+0x391/0x1790 io_uring/fdinfo.c:96
Code: 00 00 00 42 80 3c 28 00 74 0f 48 8b 7c 24 30 e8 d5 9d 22 f7 48 8b 4c 24 30 44 21 f3 48 c1 e3 02 48 03 19 48 89 d8 48 c1 e8 03 <42> 8a 04 28 84 c0 0f 85 64 02 00 00 8b 1b 89 df 44 89 f6 e8 c7 c9
RSP: 0018:ffffc900038ffc20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8880299e60d0
RDX: ffff8880262f9dc0 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900038ffd98 R08: ffffffff8ac4995f R09: 1ffff11004f01013
R10: dffffc0000000000 R11: ffffed1004f01014 R12: ffff888021153de0
R13: dffffc0000000000 R14: 0000000000003fff R15: 0000000000000001
FS: 000055555700b480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6f2394f653 CR3: 0000000029588000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 00 42 80 add %al,-0x80(%rdx)
5: 3c 28 cmp $0x28,%al
7: 00 74 0f 48 add %dh,0x48(%rdi,%rcx,1)
b: 8b 7c 24 30 mov 0x30(%rsp),%edi
f: e8 d5 9d 22 f7 call 0xf7229de9
14: 48 8b 4c 24 30 mov 0x30(%rsp),%rcx
19: 44 21 f3 and %r14d,%ebx
1c: 48 c1 e3 02 shl $0x2,%rbx
20: 48 03 19 add (%rcx),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 8a 04 28 mov (%rax,%r13,1),%al <-- trapping instruction
2e: 84 c0 test %al,%al
30: 0f 85 64 02 00 00 jne 0x29a
36: 8b 1b mov (%rbx),%ebx
38: 89 df mov %ebx,%edi
3a: 44 89 f6 mov %r14d,%esi
3d: e8 .byte 0xe8
3e: c7 (bad)
3f: c9 leave


---
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If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

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[Jens Axboe]

On 9/1/23 11:22 AM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 99d99825fc07 Merge tag 'nfs-for-6.6-1' of git://git.linux-..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12e9fc13a80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cce54b04d9a3d05b
> dashboard link: https://syzkaller.appspot.com/bug?extid=216e2ea6e0bf4a0acdd7
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1749fa10680000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10211c10680000

This should fix it:

diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index 300455b4bc12..c53678875416 100644
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -93,6 +93,8 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
struct io_uring_sqe *sqe;
unsigned int sq_idx;

+ if (ctx->flags & IORING_SETUP_NO_SQARRAY)
+ break;
sq_idx = READ_ONCE(ctx->sq_array[entry & sq_mask]);
if (sq_idx > sq_mask)
continue;

--
Jens Axboe