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* general protection fault in __dentry_path
@ 2019-01-30 10:35 syzbot
  2019-01-30 11:32 ` syzbot
  2019-02-21  4:14 ` syzbot
  0 siblings, 2 replies; 12+ messages in thread
From: syzbot @ 2019-01-30 10:35 UTC (permalink / raw)
  To: linux-fsdevel, linux-kernel, syzkaller-bugs, viro

Hello,

syzbot found the following crash on:

HEAD commit:    02495e76ded5 Add linux-next specific files for 20190130
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17e8d80f400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a2b2e9c0bc43c14d
dashboard link: https://syzkaller.appspot.com/bug?extid=7857962b4d45e602b8ad
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 445 Comm: syz-executor3 Not tainted 5.0.0-rc4-next-20190130 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__dentry_path+0x2a5/0xaa0 fs/d_path.c:344
Code: 00 00 e8 1e 9d 9f ff 48 c7 c7 68 26 81 89 e8 72 c4 14 06 e8 0d 9d 9f  
ff 48 8b 85 00 ff ff ff 48 8d 78 40 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00  
0f 85 b0 07 00 00 48 8b 85 00 ff ff ff 4c 8b 68 40
RSP: 0018:ffff8881c21bf8a8 EFLAGS: 00010207
RAX: 0000000000000005 RBX: 0000000000000000 RCX: ffffc90005b5c000
RDX: 0000000000002edf RSI: ffffffff81e27c43 RDI: 000000000000002f
RBP: ffff8881c21bf9d0 R08: ffff88806b30a040 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881c21bf9a8
R13: 0000000000000000 R14: 0000000000009674 R15: dffffc0000000000
FS:  00007f27af88b700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f722000 CR3: 0000000218991000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  dentry_path_raw+0x26/0x30 fs/d_path.c:371
  kvm_uevent_notify_change.part.0+0x213/0x440  
arch/x86/kvm/../../../virt/kvm/kvm_main.c:4050
  kvm_uevent_notify_change arch/x86/kvm/../../../virt/kvm/kvm_main.c:4017  
[inline]
  kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3355  
[inline]
  kvm_dev_ioctl+0x137a/0x1a60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3377
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:509 [inline]
  do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
  ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
  __do_sys_ioctl fs/ioctl.c:720 [inline]
  __se_sys_ioctl fs/ioctl.c:718 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458089
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f27af88ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f27af88b6d4
R13: 00000000004c0bcf R14: 00000000004d2890 R15: 00000000ffffffff
Modules linked in:
---[ end trace 1701fe85f04d676b ]---
RIP: 0010:__dentry_path+0x2a5/0xaa0 fs/d_path.c:344
Code: 00 00 e8 1e 9d 9f ff 48 c7 c7 68 26 81 89 e8 72 c4 14 06 e8 0d 9d 9f  
ff 48 8b 85 00 ff ff ff 48 8d 78 40 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00  
0f 85 b0 07 00 00 48 8b 85 00 ff ff ff 4c 8b 68 40
RSP: 0018:ffff8881c21bf8a8 EFLAGS: 00010207
RAX: 0000000000000005 RBX: 0000000000000000 RCX: ffffc90005b5c000
RDX: 0000000000002edf RSI: ffffffff81e27c43 RDI: 000000000000002f
RBP: ffff8881c21bf9d0 R08: ffff88806b30a040 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881c21bf9a8
R13: 0000000000000000 R14: 0000000000009674 R15: dffffc0000000000
FS:  00007f27af88b700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001f80f70 CR3: 0000000218991000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.

^ permalink raw reply	[flat|nested] 12+ messages in thread
* [PATCH] kvm: properly check debugfs dentry before using it
@ 2019-02-28 15:34 Greg Kroah-Hartman
  2019-02-28 16:58 ` Linus Torvalds
  2019-02-28 17:17 ` Eric Biggers
  0 siblings, 2 replies; 12+ messages in thread
From: Greg Kroah-Hartman @ 2019-02-28 15:34 UTC (permalink / raw)
  To: Linus Torvalds
  Cc: Paolo Bonzini, Radim Krčmář,
	Eric Biggers, kvm, syzbot, linux-fsdevel, linux-kernel,
	penguin-kernel, syzkaller-bugs, viro

debugfs can now report an error code if something went wrong instead of
just NULL.  So if the return value is to be used as a "real" dentry, it
needs to be checked if it is an error before dereferencing it.

This is now happening because of ff9fb72bc077 ("debugfs: return error
values, not NULL").  syzbot has found a way to trigger multiple debugfs
files attempting to be created, which fails, and then the error code
gets passed to dentry_path_raw() which obviously does not like it.

Reported-by: Eric Biggers <ebiggers@kernel.org>
Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

Linus, this should go in before 5.0-final is out, as it resolves a
problem found by syzbot.  Paolo has given his ack for me to send this
directly to you.  If you want this in [GIT PULL] format, I can do that
as well.

 virt/kvm/kvm_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4044,7 +4044,7 @@ static void kvm_uevent_notify_change(uns
 	}
 	add_uevent_var(env, "PID=%d", kvm->userspace_pid);
 
-	if (kvm->debugfs_dentry) {
+	if (!IS_ERR_OR_NULL(kvm->debugfs_dentry)) {
 		char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL);
 
 		if (p) {

^ permalink raw reply	[flat|nested] 12+ messages in thread
end of thread, other threads:[~2019-02-28 18:04 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-01-30 10:35 general protection fault in __dentry_path syzbot
2019-01-30 11:32 ` syzbot
2019-02-21  4:14 ` syzbot
2019-02-26 19:19   ` Eric Biggers
2019-02-27  8:38     ` Greg Kroah-Hartman
2019-02-28 15:08     ` [PATCH] kvm: properly check debugfs dentry before using it Greg Kroah-Hartman
2019-02-28 15:14       ` Paolo Bonzini
2019-02-28 15:32         ` Greg Kroah-Hartman
2019-02-28 15:34 Greg Kroah-Hartman
2019-02-28 16:58 ` Linus Torvalds
2019-02-28 17:17 ` Eric Biggers
2019-02-28 18:04   ` Greg Kroah-Hartman

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