WARNING: ODEBUG bug in ext4_fill_super

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: ed858b88 Add linux-next specific files for 20190826
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14209eca600000
kernel config: https://syzkaller.appspot.com/x/.config?x=ee8373cd9733e305
dashboard link: https://syzkaller.appspot.com/bug?extid=0bf8ddafbdf2c46eb6f3
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+0bf8dd...@syzkaller.appspotmail.com

EXT4-fs (loop2): corrupt root inode, run e2fsck
EXT4-fs (loop2): mount failed
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: percpu_counter hint: 0x0
WARNING: CPU: 0 PID: 12342 at lib/debugobjects.c:481
debug_print_object+0x168/0x250 lib/debugobjects.c:481
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 12342 Comm: syz-executor.2 Not tainted 5.3.0-rc6-next-20190826
#73
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2dc/0x755 kernel/panic.c:220
__warn.cold+0x2f/0x3c kernel/panic.c:581
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:179 [inline]
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:debug_print_object+0x168/0x250 lib/debugobjects.c:481
Code: dd 60 6c e6 87 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 b5 00 00 00 48
8b 14 dd 60 6c e6 87 48 c7 c7 c0 61 e6 87 e8 20 31 01 fe <0f> 0b 83 05 f3
67 83 06 01 48 83 c4 20 5b 41 5c 41 5d 41 5e 5d c3
RSP: 0018:ffff88806c9ff938 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000040000 RSI: ffffffff815bd606 RDI: ffffed100d93ff19
RBP: ffff88806c9ff978 R08: ffff888067d48140 R09: ffffed1015d04109
R10: ffffed1015d04108 R11: ffff8880ae820847 R12: 0000000000000001
R13: ffffffff8935e800 R14: 0000000000000000 R15: ffff88806903c818
__debug_check_no_obj_freed lib/debugobjects.c:963 [inline]
debug_check_no_obj_freed+0x2d4/0x43f lib/debugobjects.c:994
kfree+0xf8/0x2c0 mm/slab.c:3755
ext4_fill_super+0x8cb/0xcc80 fs/ext4/super.c:4684
mount_bdev+0x304/0x3c0 fs/super.c:1407
ext4_mount+0x35/0x40 fs/ext4/super.c:6019
legacy_get_tree+0x113/0x220 fs/fs_context.c:651
vfs_get_tree+0x8f/0x380 fs/super.c:1482
do_new_mount fs/namespace.c:2796 [inline]
do_mount+0x13b3/0x1c30 fs/namespace.c:3116
ksys_mount+0xdb/0x150 fs/namespace.c:3325
__do_sys_mount fs/namespace.c:3339 [inline]
__se_sys_mount fs/namespace.c:3336 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3336
do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c2ca
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d 8d fb ff c3 66 2e 0f
1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 0f 83 7a 8d fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fa684517a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fa684517b40 RCX: 000000000045c2ca
RDX: 00007fa684517ae0 RSI: 0000000020000000 RDI: 00007fa684517b00
RBP: 0000000000001000 R08: 00007fa684517b40 R09: 00007fa684517ae0
R10: 0000000000000001 R11: 0000000000000206 R12: 0000000000000003
R13: 00000000004c89d6 R14: 00000000004df8f8 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[Nick Desaulniers]

Dmitry,
Any idea how clang-built-linux got CC'ed on this? Is syzcaller
running clang builds, yet? (this looks like a GCC build)

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--
Thanks,
~Nick Desaulniers

[Dmitry Vyukov]

On Fri, Aug 30, 2019 at 12:42 PM 'Nick Desaulniers' via syzkaller-bugs
<syzkall...@googlegroups.com> wrote:
>
> Dmitry,
> Any idea how clang-built-linux got CC'ed on this? Is syzcaller
> running clang builds, yet? (this looks like a GCC build)

syzbot always uses get_maintainers:

$ ./scripts/get_maintainer.pl -f fs/ext4/super.c
"Theodore Ts'o" <ty...@mit.edu> (maintainer:EXT4 FILE SYSTEM)
Andreas Dilger <adilger...@dilger.ca> (maintainer:EXT4 FILE SYSTEM)
linux...@vger.kernel.org (open list:EXT4 FILE SYSTEM)
linux-...@vger.kernel.org (open list)
clang-bu...@googlegroups.com (open list:CLANG/LLVM BUILD SUPPORT)

> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bug...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/CAKwvOdkAaFKr5gDw31uRzGoEC1JaJGNnrnAX_ysx9kH7dKx19Q%40mail.gmail.com.

[Theodore Y. Ts'o]

#syz invalid

This has already been fixed in the latest linux-next

[Eric Biggers]

On Fri, Aug 30, 2019 at 12:46:21PM -0700, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Fri, Aug 30, 2019 at 12:42 PM 'Nick Desaulniers' via syzkaller-bugs
> <syzkall...@googlegroups.com> wrote:
> >
> > Dmitry,
> > Any idea how clang-built-linux got CC'ed on this? Is syzcaller
> > running clang builds, yet? (this looks like a GCC build)
>
> syzbot always uses get_maintainers:
>
> $ ./scripts/get_maintainer.pl -f fs/ext4/super.c
> "Theodore Ts'o" <ty...@mit.edu> (maintainer:EXT4 FILE SYSTEM)
> Andreas Dilger <adilger...@dilger.ca> (maintainer:EXT4 FILE SYSTEM)
> linux...@vger.kernel.org (open list:EXT4 FILE SYSTEM)
> linux-...@vger.kernel.org (open list)
> clang-bu...@googlegroups.com (open list:CLANG/LLVM BUILD SUPPORT)
>

CLANG/LLVM BUILD SUPPORT
L: clang-bu...@googlegroups.com
W: https://clangbuiltlinux.github.io/
B: https://github.com/ClangBuiltLinux/linux/issues
C: irc://chat.freenode.net/clangbuiltlinux
S: Supported
K: \b(?i:clang|llvm)\b

So, clang-built-linux has volunteered to maintain every file that contains the
word "clang" or "llvm" anywhere in its contents :-)

$ grep clang fs/ext4/super.c
(void) ei; /* shut up clang warning if !CONFIG_LOCKDEP */

- Eric