kernel panic: smack: Failed to initialize cipso DOI.

[Eric Biggers]

Hi Casey,

On Mon, Mar 30, 2020 at 06:51:18AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    1b649e0b Merge git://git.kernel.org/pub/scm/linux/kernel/g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14957099e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4ac76c43beddbd9
> dashboard link: https://syzkaller.appspot.com/bug?extid=89731ccb6fec15ce1c22
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1202c375e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1390bb03e00000
> 
> The bug was bisected to:
> 
> commit a9d2d53a788a9c5bc8a7d1b4ea7857b68e221357
> Author: Ken Cox <jkc at redhat.com>
> Date:   Tue Nov 15 19:00:37 2016 +0000
> 
>     ixgbe: test for trust in macvlan adjustments for VF
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13cb06f3e00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=102b06f3e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17cb06f3e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+89731ccb6fec15ce1c22 at syzkaller.appspotmail.com
> Fixes: a9d2d53a788a ("ixgbe: test for trust in macvlan adjustments for VF")
> 
> RSP: 002b:00007ffebd499a38 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007ffebd499a40 RCX: 00000000004404e9
> RDX: 0000000000000014 RSI: 0000000020000040 RDI: 0000000000000003
> RBP: 0000000000000004 R08: 0000000000000001 R09: 00007ffebd490031
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401dd0
> R13: 0000000000401e60 R14: 0000000000000000 R15: 0000000000000000
> Kernel panic - not syncing: smack:  Failed to initialize cipso DOI.
> CPU: 1 PID: 7197 Comm: syz-executor480 Not tainted 5.6.0-rc7-syzkaller #0
> 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+0x1e9/0x30e lib/dump_stack.c:118
>  panic+0x264/0x7a0 kernel/panic.c:221
>  smk_cipso_doi+0x4d8/0x4e0 security/smack/smackfs.c:698
>  smk_write_doi+0x123/0x190 security/smack/smackfs.c:1595
>  __vfs_write+0xa7/0x710 fs/read_write.c:494
>  vfs_write+0x271/0x570 fs/read_write.c:558
>  ksys_write+0x115/0x220 fs/read_write.c:611
>  do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4404e9
> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffebd499a38 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007ffebd499a40 RCX: 00000000004404e9
> RDX: 0000000000000014 RSI: 0000000020000040 RDI: 0000000000000003
> RBP: 0000000000000004 R08: 0000000000000001 R09: 00007ffebd490031
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401dd0
> R13: 0000000000401e60 R14: 0000000000000000 R15: 0000000000000000
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 

This means that writing to /smack/doi will panic the kernel if kmalloc fails.

Why doesn't it handle errors?  Is this really an unrecoverable situation?

- Eric