[moderation] [audit?] BUG: unable to handle kernel NULL pointer dereference in kauditd_hold_skb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e6ebf0117218 Merge tag 'mm-hotfixes-stable-2024-04-26-13-3..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10eb28a7180000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ebf23eff17a043d
dashboard link: https://syzkaller.appspot.com/bug?extid=d6593a14befc47870cd1
compiler: arm-linux-gnueabi-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm
CC: [au...@vger.kernel.org epa...@redhat.com linux-...@vger.kernel.org pa...@paul-moore.com]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/8ead8862021c/non_bootable_disk-e6ebf011.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b83a361a7d5/vmlinux-e6ebf011.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a40e7dbb3372/zImage-e6ebf011.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6593a...@syzkaller.appspotmail.com

kauditd_printk_skb: 13 callbacks suppressed
8<--- cut here ---
Unable to handle kernel NULL pointer dereference at virtual address 00000000 when read
[00000000] *pgd=80000080004003, *pmd=00000000
Internal error: Oops: 207 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 30 Comm: kauditd Not tainted 6.9.0-rc5-syzkaller #0
Hardware name: ARM-Versatile Express
PC is at printk_get_level include/linux/printk.h:21 [inline]
PC is at printk_parse_prefix+0xc/0x90 kernel/printk/printk.c:2137
LR is at printk_sprint+0x10c/0x164 kernel/printk/printk.c:2177
pc : [<802bc1c4>] lr : [<802bc354>] psr: 60000093
sp : df8d9d70 ip : df8d9d80 fp : df8d9d7c
r10: 8262a180 r9 : 00000000 r8 : 00000000
r7 : df8d9dc8 r6 : 00000000 r5 : 00000000 r4 : 00000000
r3 : df8d9ebc r2 : 00000000 r1 : 00000000 r0 : 00000000
Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
Control: 30c5387d Table: 85044f00 DAC: fffffffd
Register r0 information: NULL pointer
Register r1 information: NULL pointer
Register r2 information: NULL pointer
Register r3 information: 2-page vmalloc region starting at 0xdf8d8000 allocated at kernel_clone+0xac/0x3cc kernel/fork.c:2797
Register r4 information: NULL pointer
Register r5 information: NULL pointer
Register r6 information: NULL pointer
Register r7 information: 2-page vmalloc region starting at 0xdf8d8000 allocated at kernel_clone+0xac/0x3cc kernel/fork.c:2797
Register r8 information: NULL pointer
Register r9 information: NULL pointer
Register r10 information: non-slab/vmalloc memory
Register r11 information: 2-page vmalloc region starting at 0xdf8d8000 allocated at kernel_clone+0xac/0x3cc kernel/fork.c:2797
Register r12 information: 2-page vmalloc region starting at 0xdf8d8000 allocated at kernel_clone+0xac/0x3cc kernel/fork.c:2797
Process kauditd (pid: 30, stack limit = 0xdf8d8000)
Stack: (0xdf8d9d70 to 0xdf8da000)
9d60: df8d9d9c df8d9d80 802bc354 802bc1c4
9d80: 00000000 00000000 dddc5595 00000000 df8d9e24 df8d9da0 802bc5b8 802bc254
9da0: 81fce634 df8d9ebc 0000001e 0000000f 5c342488 00000004 0000001e 81fce634
9dc0: 60000013 00000005 00000000 df8d9ebc 8263bf58 00000000 00000000 8262a22c
9de0: 60000093 3fffe33d 00000000 75613501 00746964 e6fa66a7 802ba680 00000000
9e00: ffffffff 82622ec4 00000000 00000000 00000000 81fce634 df8d9e64 df8d9e28
9e20: 802bd6e0 802bc3b8 df8d9ebc 8262a1ac 82604d40 00000000 81a10a68 82ee0c00
9e40: 850c0000 00000000 8033fadc 844c9e40 00000000 00000000 df8d9e7c df8d9e68
9e60: 802bd87c 802bd5e8 df8d9ebc df8d9e78 df8d9e9c df8d9e80 802be8b8 802bd860
9e80: 818921f4 818ccb80 844c9e40 ffffff91 df8d9eb4 df8d9ea0 818a5160 802be850
9ea0: df8d9ebc e6fa66a7 df8d9ee4 df8d9ec8 8034028c 818a513c 81fce634 00000579
9ec0: 850c0010 00000000 826fb6ec 844c9e40 00000000 8033fadc df8d9f24 df8d9ee8
9ee0: 8033fcfc 803401bc df8d9f04 00000001 00000000 8289fa50 df8d9f24 826fb6ec
9f00: 8289f9f8 00000000 00000000 82ea2380 00000000 00000000 df8d9f84 df8d9f28
9f20: 803405b4 8033fc0c 8033fadc 803401b0 8027cae4 803401b0 8033fa84 8033fadc
9f40: 00000000 82ee0c00 802a4d14 df8d9f4c df8d9f4c e6fa66a7 df8d9f84 82ea2280
9f60: 82ee0c00 80340334 00000000 82ea2380 df819e50 00000000 df8d9fac df8d9f88
9f80: 80270024 80340340 82ea2280 8026ff20 00000000 00000000 00000000 00000000
9fa0: 00000000 df8d9fb0 80200104 8026ff2c 00000000 00000000 00000000 00000000
9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Call trace:
[<802bc1b8>] (printk_parse_prefix) from [<802bc354>] (printk_sprint+0x10c/0x164 kernel/printk/printk.c:2177)
[<802bc248>] (printk_sprint) from [<802bc5b8>] (vprintk_store+0x20c/0x450 kernel/printk/printk.c:2279)
r7:00000000 r6:dddc5595 r5:00000000 r4:00000000
[<802bc3ac>] (vprintk_store) from [<802bd6e0>] (vprintk_emit+0x104/0x278 kernel/printk/printk.c:2329)
r10:81fce634 r9:00000000 r8:00000000 r7:00000000 r6:82622ec4 r5:ffffffff
r4:00000000
[<802bd5dc>] (vprintk_emit) from [<802bd87c>] (vprintk_default+0x28/0x30 kernel/printk/printk.c:2363)
r10:00000000 r9:00000000 r8:844c9e40 r7:8033fadc r6:00000000 r5:850c0000
r4:82ee0c00
[<802bd854>] (vprintk_default) from [<802be8b8>] (vprintk+0x74/0x94 kernel/printk/printk_safe.c:45)
[<802be844>] (vprintk) from [<818a5160>] (_printk+0x34/0x58 kernel/printk/printk.c:2373)
r6:ffffff91 r4:844c9e40
[<818a512c>] (_printk) from [<8034028c>] (kauditd_printk_skb kernel/audit.c:546 [inline])
[<818a512c>] (_printk) from [<8034028c>] (kauditd_hold_skb+0xdc/0xf8 kernel/audit.c:581)
r3:00000000 r2:850c0010 r1:00000579 r0:81fce634
[<803401b0>] (kauditd_hold_skb) from [<8033fcfc>] (kauditd_send_queue+0xfc/0x16c kernel/audit.c:766)
r7:8033fadc r6:00000000 r5:844c9e40 r4:826fb6ec
[<8033fc00>] (kauditd_send_queue) from [<803405b4>] (kauditd_thread+0x280/0x2d8 kernel/audit.c:890)
r10:00000000 r9:00000000 r8:82ea2380 r7:00000000 r6:00000000 r5:8289f9f8
r4:826fb6ec
[<80340334>] (kauditd_thread) from [<80270024>] (kthread+0x104/0x134 kernel/kthread.c:388)
r10:00000000 r9:df819e50 r8:82ea2380 r7:00000000 r6:80340334 r5:82ee0c00
r4:82ea2280
[<8026ff20>] (kthread) from [<80200104>] (ret_from_fork+0x14/0x30 arch/arm/kernel/entry-common.S:134)
Exception stack(0xdf8d9fb0 to 0xdf8d9ff8)
9fa0: 00000000 00000000 00000000 00000000
9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:8026ff20 r4:82ea2280
Code: e89da800 e1a0c00d e92dd800 e24cb004 (e5d03000)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: e89da800 ldm sp, {fp, sp, pc}
4: e1a0c00d mov ip, sp
8: e92dd800 push {fp, ip, lr, pc}
c: e24cb004 sub fp, ip, #4
* 10: e5d03000 ldrb r3, [r0] <-- trapping instruction


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