[syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    2d8308bf5b67 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1383bcdf980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=99a5586995ec03b2
dashboard link: https://syzkaller.appspot.com/bug?extid=b95d0c98f01e7a95da72
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1189c344580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=103b94f8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/66039e873a32/disk-2d8308bf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/60744ba3f743/vmlinux-2d8308bf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/25731ba013ad/bzImage-2d8308bf.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b95d0c98f01e7a95da72@syzkaller.appspotmail.com

RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007fffecdd9167 R09: 00007f4106f40032
R10: 0000000000000005 R11: 0000000000000246 R12: 00007f4106f46618
R13: 00007fffecdd95a8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5829 Comm: syz-executor520 Not tainted 6.13.0-rc2-syzkaller-00362-g2d8308bf5b67 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
RIP: 0010:gpiolib_seq_stop+0x4c/0xe0 drivers/gpio/gpiolib.c:5067
Code: 48 c1 ea 03 80 3c 02 00 0f 85 98 00 00 00 48 8b 9b e0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 04 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 60 8b
RSP: 0018:ffffc90003e1fa58 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88802463a018
RDX: 0000000000000000 RSI: ffffffff84cc96be RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: ffffffff8df7c5d3 R11: 0000000000000001 R12: ffffffff8bb596a0
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90003e1fc40
FS:  0000555557ff9380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e43c381608 CR3: 0000000076408000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 traverse.part.0.constprop.0+0x2bd/0x640 fs/seq_file.c:131
 traverse fs/seq_file.c:98 [inline]
 seq_read_iter+0x934/0x12b0 fs/seq_file.c:195
 seq_read+0x39f/0x4e0 fs/seq_file.c:162
 full_proxy_read+0xfb/0x1b0 fs/debugfs/file.c:351
 vfs_read+0x1df/0xbe0 fs/read_write.c:563
 ksys_pread64 fs/read_write.c:756 [inline]
 __do_sys_pread64 fs/read_write.c:764 [inline]
 __se_sys_pread64 fs/read_write.c:761 [inline]
 __x64_sys_pread64+0x1f6/0x250 fs/read_write.c:761
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4106edb2e9
Code: 48 83 c4 28 c3 e8 17 1a 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:00007fffecdd93c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000011
RAX: ffffffffffffffda RBX: 00007fffecdd93d0 RCX: 00007f4106edb2e9
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007fffecdd9167 R09: 00007f4106f40032
R10: 0000000000000005 R11: 0000000000000246 R12: 00007f4106f46618
R13: 00007fffecdd95a8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:gpiolib_seq_stop+0x4c/0xe0 drivers/gpio/gpiolib.c:5067
Code: 48 c1 ea 03 80 3c 02 00 0f 85 98 00 00 00 48 8b 9b e0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 04 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 60 8b
RSP: 0018:ffffc90003e1fa58 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88802463a018
RDX: 0000000000000000 RSI: ffffffff84cc96be RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: ffffffff8df7c5d3 R11: 0000000000000001 R12: ffffffff8bb596a0
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90003e1fc40
FS:  0000555557ff9380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 0000000076408000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	48 c1 ea 03          	shr    $0x3,%rdx
   4:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   8:	0f 85 98 00 00 00    	jne    0xa6
   e:	48 8b 9b e0 00 00 00 	mov    0xe0(%rbx),%rbx
  15:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  1c:	fc ff df
  1f:	48 8d 7b 04          	lea    0x4(%rbx),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2e:	48 89 f8             	mov    %rdi,%rax
  31:	83 e0 07             	and    $0x7,%eax
  34:	83 c0 03             	add    $0x3,%eax
  37:	38 d0                	cmp    %dl,%al
  39:	7c 04                	jl     0x3f
  3b:	84 d2                	test   %dl,%dl
  3d:	75 60                	jne    0x9f
  3f:	8b                   	.byte 0x8b


---
This report is generated by a bot. It may contain errors.
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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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Re: [syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[Edward Adam Davis]

#syz test: https://github.com/ea1davis/linux gpio/syz

Re: [syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: lock held when returning to user space in gpiolib_seq_start

RBP: 00007fe66f38b090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 00007fe66e775fa0 R15: 00007ffe92372dd8
 </TASK>
================================================
WARNING: lock held when returning to user space!
6.12.0-syzkaller-10299-gc1f7eb90d8d5 #0 Not tainted
------------------------------------------------
syz.0.18/6685 is leaving the kernel with locks still held!
1 lock held by syz.0.18/6685:
 #0: ffffffff8e96d590 (gpio_devices_srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:158 [inline]
 #0: ffffffff8e96d590 (gpio_devices_srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:249 [inline]
 #0: ffffffff8e96d590 (gpio_devices_srcu){.+.+}-{0:0}, at: gpiolib_seq_start+0x13e/0x270 drivers/gpio/gpiolib.c:5039


Tested on:

commit:         c1f7eb90 fs/seq_file: Exit the subsequent process when..
git tree:       https://github.com/ea1davis/linux gpio/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=12dfb4f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89
dashboard link: https://syzkaller.appspot.com/bug?extid=b95d0c98f01e7a95da72
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.

Re: [syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[Edward Adam Davis]

#syz test: https://github.com/ea1davis/linux gpio/syz

Re: [syzbot] [gpio?] general protection fault in gpiolib_seq_stop

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+b95d0c98f01e7a95da72@syzkaller.appspotmail.com
Tested-by: syzbot+b95d0c98f01e7a95da72@syzkaller.appspotmail.com

Tested on:

commit:         36a3a495 fs/seq_file: Exit the subsequent process when..
git tree:       https://github.com/ea1davis/linux gpio/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=160a8b44580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89
dashboard link: https://syzkaller.appspot.com/bug?extid=b95d0c98f01e7a95da72
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[PATCH] fs/seq_file: Exit the subsequent process when seq start fails

[Edward Adam Davis]

syzbot report a null-ptr-deref in gpiolib_seq_stop. [1]

syzbot uses "echo 2 > /proc/thread-self/fail-nth", and in the current thread,
the second memory allocation will trigger a failure.
That is to say, the memory allocation for priv in gpiolib_seq_start() fails,
so m->private is not initialized, which eventually leads to a null pointer
dereference to m->private in gpiolib_seq_stop().

Because this type of problem is recurring, it is best to handle it in the
upper layer of the gpio driver, that is, in fs/seq_file.c, and judge the
pointer returned after m->op->start() returns. If its value is null, exit
the subsequent process.This failure does not affect the next execution of
traverse(), so 0 is returned here.

[1]
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5829 Comm: syz-executor520 Not tainted 6.13.0-rc2-syzkaller-00362-g2d8308bf5b67 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
RIP: 0010:gpiolib_seq_stop+0x4c/0xe0 drivers/gpio/gpiolib.c:5067
Code: 48 c1 ea 03 80 3c 02 00 0f 85 98 00 00 00 48 8b 9b e0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 04 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 60 8b
RSP: 0018:ffffc90003e1fa58 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88802463a018
RDX: 0000000000000000 RSI: ffffffff84cc96be RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: ffffffff8df7c5d3 R11: 0000000000000001 R12: ffffffff8bb596a0
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90003e1fc40
FS:  0000555557ff9380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e43c381608 CR3: 0000000076408000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 traverse.part.0.constprop.0+0x2bd/0x640 fs/seq_file.c:131
 traverse fs/seq_file.c:98 [inline]
 seq_read_iter+0x934/0x12b0 fs/seq_file.c:195
 seq_read+0x39f/0x4e0 fs/seq_file.c:162
 full_proxy_read+0xfb/0x1b0 fs/debugfs/file.c:351
 vfs_read+0x1df/0xbe0 fs/read_write.c:563
 ksys_pread64 fs/read_write.c:756 [inline]
 __do_sys_pread64 fs/read_write.c:764 [inline]
 __se_sys_pread64 fs/read_write.c:761 [inline]
 __x64_sys_pread64+0x1f6/0x250 fs/read_write.c:761
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported-by: syzbot+b95d0c98f01e7a95da72@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b95d0c98f01e7a95da72
Tested-by: syzbot+b95d0c98f01e7a95da72@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 fs/seq_file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 8bbb1ad46335..130424bbcf7d 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -104,6 +104,9 @@ static int traverse(struct seq_file *m, loff_t offset)
 			return -ENOMEM;
 	}
 	p = m->op->start(m, &m->index);
+	if (!p && !m->private)
+		return 0;
+
 	while (p) {
 		error = PTR_ERR(p);
 		if (IS_ERR(p))
-- 
2.47.0