Re: [PATCH net v5 0/2] net,bpf: fix null-ptr-deref in xdp_master_redirect() for bonding and add selftest

On Mon, Mar 9, 2026 at 10:41 AM Jiayuan Chen [off-list ref] wrote:

March 9, 2026 at 15:46, "Eric Dumazet" <edumazet@google.com mailto:edumazet@google.com?to=%22Eric%20Dumazet%22%20%3Cedumazet%40google.com%3E > wrote:

quoted

On Mon, Mar 9, 2026 at 4:07 AM Jiayuan Chen [off-list ref] wrote:

quoted

syzkaller reported a kernel panic [1] with the following crash stack:

 Call Trace:
 BUG: unable to handle page fault for address: ffff8ebd08580000
 PF: supervisor write access in kernel mode
 PF: error_code(0x0002) - not-present page
 PGD 11f201067 P4D 11f201067 PUD 0
 Oops: Oops: 0002 [#1] SMP PTI
 CPU: 2 UID: 0 PID: 451 Comm: test_progs Not tainted 6.19.0+ #161 PREEMPT_RT
 RIP: 0010:bond_rr_gen_slave_id+0x90/0xd0
 RSP: 0018:ffffd3f4815f3448 EFLAGS: 00010246
 RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffff8ebc8728b17e
 RDX: 0000000000000000 RSI: ffffd3f4815f3538 RDI: ffff8ebc8abcce40
 RBP: ffffd3f4815f3460 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000000 R12: ffffd3f4815f3538
 R13: ffff8ebc8abcce40 R14: ffff8ebc8728b17f R15: ffff8ebc8728b170
 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffff8ebd08580000 CR3: 000000010a808006 CR4: 0000000000770ef0
 PKRU: 55555554
 Call Trace:
 <TASK>
 bond_xdp_get_xmit_slave+0xc0/0x240
 xdp_master_redirect+0x74/0xc0
 bpf_prog_run_generic_xdp+0x2f2/0x3f0
 do_xdp_generic+0x1fd/0x3d0
 __netif_receive_skb_core.constprop.0+0x30d/0x1220
 __netif_receive_skb_list_core+0xfc/0x250
 netif_receive_skb_list_internal+0x20c/0x3d0
 ? eth_type_trans+0x137/0x160
 netif_receive_skb_list+0x25/0x140
 xdp_test_run_batch.constprop.0+0x65b/0x6e0
 bpf_test_run_xdp_live+0x1ec/0x3b0
 bpf_prog_test_run_xdp+0x49d/0x6e0
 __sys_bpf+0x446/0x27b0
 __x64_sys_bpf+0x1a/0x30
 x64_sys_call+0x146c/0x26e0
 do_syscall_64+0xd3/0x1510
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Please, can you always provide symbols in such traces ?
You can use scripts/decode_stacktrace.sh to make the trace really
nice, instead of ugly.

Hi Eric,

Thank you for the suggestion. I didn't include the fully decoded stack
trace in the cover letter because the syzkaller report already contains
the complete information. You can find it here if needed:

https://syzkaller.appspot.com/text?tag=CrashReport&x=15448952580000
https://syzkaller.appspot.com/bug?extid=80e046b8da2820b6ba73

Exactly.

Either copy the syzbot stack traces when they have the symbols,
or do not copy them if they don't have them, a link to them is just good enough.