kernel BUG at arch/x86/mm/physaddr.c:LINE! (4)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 36a44bcd Merge branch 'bnxt_en-shutdown-and-kexec-kdump-re..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=12524265e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=768cc3d3e277cc16
dashboard link: https://syzkaller.appspot.com/bug?extid=1f4d90ead370d72e450b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123d9de9e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1648fe09e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1f4d90...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at arch/x86/mm/physaddr.c:28!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 9873 Comm: syz-executor039 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__phys_addr+0xb3/0x120 arch/x86/mm/physaddr.c:28
Code: 09 4c 89 e3 31 ff 48 d3 eb 48 89 de e8 36 e2 40 00 48 85 db 75 0f e8 8c e0 40 00 4c 89 e0 5b 41 5c 41 5d 5d c3 e8 7d e0 40 00 <0f> 0b e8 76 e0 40 00 48 c7 c0 10 50 a7 89 48 ba 00 00 00 00 00 fc
RSP: 0018:ffffc90005b47490 EFLAGS: 00010093
RAX: ffff8880944f4600 RBX: 0000000002777259 RCX: ffffffff8134ad32
RDX: 0000000000000000 RSI: ffffffff8134ad93 RDI: 0000000000000006
RBP: ffffc90005b474a8 R08: ffff8880944f4600 R09: ffffed1015d2707c
R10: ffffed1015d2707b R11: ffff8880ae9383db R12: 0000778002777259
R13: 0000000082777259 R14: ffff88809a765000 R15: 0000000000000010
FS: 0000000001436880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200004c0 CR3: 0000000096da8000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
virt_to_head_page include/linux/mm.h:721 [inline]
virt_to_cache mm/slab.h:472 [inline]
kfree+0x7b/0x2c0 mm/slab.c:3749
audit_free_lsm_field kernel/auditfilter.c:76 [inline]
audit_free_rule kernel/auditfilter.c:91 [inline]
audit_data_to_entry+0xb7b/0x25f0 kernel/auditfilter.c:603
audit_rule_change+0x6b5/0x1130 kernel/auditfilter.c:1130
audit_receive_msg+0xda5/0x28b0 kernel/audit.c:1368
audit_receive+0x114/0x230 kernel/audit.c:1513
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x59e/0x7e0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:672
____sys_sendmsg+0x753/0x880 net/socket.c:2343
___sys_sendmsg+0x100/0x170 net/socket.c:2397
__sys_sendmsg+0x105/0x1d0 net/socket.c:2430
__do_sys_sendmsg net/socket.c:2439 [inline]
__se_sys_sendmsg net/socket.c:2437 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2437
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4401a9
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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd66553d28 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401a9
RDX: 0000000000000000 RSI: 00000000200004c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a30
R13: 0000000000401ac0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 1e4db35053a9d748 ]---
RIP: 0010:__phys_addr+0xb3/0x120 arch/x86/mm/physaddr.c:28
Code: 09 4c 89 e3 31 ff 48 d3 eb 48 89 de e8 36 e2 40 00 48 85 db 75 0f e8 8c e0 40 00 4c 89 e0 5b 41 5c 41 5d 5d c3 e8 7d e0 40 00 <0f> 0b e8 76 e0 40 00 48 c7 c0 10 50 a7 89 48 ba 00 00 00 00 00 fc
RSP: 0018:ffffc90005b47490 EFLAGS: 00010093
RAX: ffff8880944f4600 RBX: 0000000002777259 RCX: ffffffff8134ad32
RDX: 0000000000000000 RSI: ffffffff8134ad93 RDI: 0000000000000006
RBP: ffffc90005b474a8 R08: ffff8880944f4600 R09: ffffed1015d2707c
R10: ffffed1015d2707b R11: ffff8880ae9383db R12: 0000778002777259
R13: 0000000082777259 R14: ffff88809a765000 R15: 0000000000000010
FS: 0000000001436880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200004c0 CR3: 0000000096da8000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[Paul Moore]

Ugh, I think I see the problem.

In audit_data_to_entry() the code sets both an audit_field->type and
an audit_field->val near the top of the big for-loop (lines 466 and
467 in Linus' tree as of now); if the type happens to be one of the
types which cause the lsm_str field to be kfree()'d (see
audit_free_lsm_field()), then we could run into problems if we end up
following an error path in audit_data_to_entry() before the lsm_str
field is populated with an actual string.

If the above reasoning proves to be correct, it looks like the problem
was caused by 219ca39427bf ("audit: use union for audit_field values
since they are mutually exclusive").

I'll see about working up a fix.

--
paul moore
www.paul-moore.com