[syzbot] [bpf?] [net?] BUG: unable to handle kernel NULL pointer dereference in __build_skb_around

From: syzbot
Date: Wed Mar 15 2023 - 08:03:54 EST

Hello,

syzbot found the following issue on:

HEAD commit: 3c2611bac08a selftests/bpf: Fix trace_virtqueue_add_sgs te..
git tree: bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1026d472c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
dashboard link: https://syzkaller.appspot.com/bug?extid=e1d1b65f7c32f2a86a9f
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15826bc6c80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15cd12e2c80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/36a32f4d222a/disk-3c2611ba.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f5c0da04f143/vmlinux-3c2611ba.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ae2ca9bce51a/bzImage-3c2611ba.xz

The issue was bisected to:

commit 9c94bbf9a87b264294f42e6cc0f76d87854733ec
Author: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
Date: Mon Mar 13 21:55:52 2023 +0000

xdp: recycle Page Pool backed skbs built from XDP frames

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11deec2ac80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=13deec2ac80000
console output: https://syzkaller.appspot.com/x/log.txt?x=15deec2ac80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e1d1b65f7c32f2a86a9f@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 9c94bbf9a87b ("xdp: recycle Page Pool backed skbs built from XDP frames")

BUG: kernel NULL pointer dereference, address: 0000000000000d28
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 7b741067 P4D 7b741067 PUD 7c1ca067 PMD 0
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5080 Comm: syz-executor371 Not tainted 6.2.0-syzkaller-13030-g3c2611bac08a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:memset_erms+0xd/0x20 arch/x86/lib/memset_64.S:66
Code: 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 66 0f 1f 00 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 66 0f 1f
RSP: 0018:ffffc90003baf730 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888028b94000 RCX: 0000000000000020
RDX: 0000000000000020 RSI: 0000000000000000 RDI: 0000000000000d28
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000d28
R10: ffffed100517281c R11: 0000000000094001 R12: 0000000000000d48
R13: 0000000000000d28 R14: 0000000000000f68 R15: 0000000000000100
FS: 0000555555979300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000d28 CR3: 0000000028e2d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__finalize_skb_around net/core/skbuff.c:321 [inline]
__build_skb_around+0x232/0x3a0 net/core/skbuff.c:379
build_skb_around+0x32/0x290 net/core/skbuff.c:444
__xdp_build_skb_from_frame+0x121/0x760 net/core/xdp.c:622
xdp_recv_frames net/bpf/test_run.c:248 [inline]
xdp_test_run_batch net/bpf/test_run.c:334 [inline]
bpf_test_run_xdp_live+0x1289/0x1930 net/bpf/test_run.c:362
bpf_prog_test_run_xdp+0xa05/0x14e0 net/bpf/test_run.c:1418
bpf_prog_test_run kernel/bpf/syscall.c:3675 [inline]
__sys_bpf+0x1598/0x5100 kernel/bpf/syscall.c:5028
__do_sys_bpf kernel/bpf/syscall.c:5114 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5112 [inline]
__x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5112
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f320b4efca9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd2c9924d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f320b4efca9
RDX: 0000000000000048 RSI: 0000000020000080 RDI: 000000000000000a
RBP: 00007f320b4b3e50 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f320b4b3ee0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
CR2: 0000000000000d28
---[ end trace 0000000000000000 ]---
RIP: 0010:memset_erms+0xd/0x20 arch/x86/lib/memset_64.S:66
Code: 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 66 0f 1f 00 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 66 0f 1f
RSP: 0018:ffffc90003baf730 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888028b94000 RCX: 0000000000000020
RDX: 0000000000000020 RSI: 0000000000000000 RDI: 0000000000000d28
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000d28
R10: ffffed100517281c R11: 0000000000094001 R12: 0000000000000d48
R13: 0000000000000d28 R14: 0000000000000f68 R15: 0000000000000100
FS: 0000555555979300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000d28 CR3: 0000000028e2d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 48 0f af c6 imul %rsi,%rax
4: f3 48 ab rep stos %rax,%es:(%rdi)
7: 89 d1 mov %edx,%ecx
9: f3 aa rep stos %al,%es:(%rdi)
b: 4c 89 c8 mov %r9,%rax
e: c3 retq
f: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
16: 00 00 00 00
1a: 66 90 xchg %ax,%ax
1c: 66 0f 1f 00 nopw (%rax)
20: 49 89 f9 mov %rdi,%r9
23: 40 88 f0 mov %sil,%al
26: 48 89 d1 mov %rdx,%rcx
* 29: f3 aa rep stos %al,%es:(%rdi) <-- trapping instruction
2b: 4c 89 c8 mov %r9,%rax
2e: c3 retq
2f: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
36: 00 00 00 00
3a: 66 90 xchg %ax,%ax
3c: 66 data16
3d: 0f .byte 0xf
3e: 1f (bad)


---
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