On 04/19/2018 04:26 AM, Liu, Changcheng wrote: > Hit below panic due to skb is NULL, WARN wrong skb first. > if __tcp_retransmit_skb return failure e.g. -EAGAIN, it > needn't do further action in tcp_retransmit_skb. > > gdb vmlinux > Reading symbols from vmlinux...done. > (gdb) p &((struct tcp_skb_cb *) \ > &(((struct sk_buff *)0)->cb[0]))->tcp_gso_segs > $1 = (u16 *) 0x30 <irq_stack_union+48> > > [ 9040.917533] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000030 > [ 9040.926279] IP: tcp_retransmit_skb+0x5c/0xc0 > [ 9040.931043] PGD 0 P4D 0 > [ 9040.933865] Oops: 0000 [#1] PREEMPT SMP PTI > [ 9040.972151] RIP: 0010:tcp_retransmit_skb+0x5c/0xc0 > [ 9040.977496] RSP: 0018:ffff8802bec83e40 EFLAGS: 00010202 > [ 9041.062527] Call Trace: > [ 9041.065250] <IRQ> > [ 9041.067489] tcp_retransmit_timer+0x481/0x820 > [ 9041.077697] tcp_write_timer_handler+0xe9/0x230 > [ 9041.082751] tcp_write_timer+0x75/0x80 > [ 9041.086932] call_timer_fn+0x29/0x150 > [ 9041.091018] run_timer_softirq+0x411/0x460 > [ 9041.105017] __do_softirq+0x115/0x311 > [ 9041.109103] irq_exit+0xb0/0xc0 > [ 9041.112605] smp_apic_timer_interrupt+0x67/0x140 > > Signed-off-by: Liu Changcheng <changcheng....@intel.com> >
On which kernel have you seen this problem ? In networking, we want patches with a 'Fixes:' tag to clearly identify which patch added a regression. Anyway your patch comes too late I guess https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=bffd168c3fc5cc7d2bad4c668fa90e7a9010db4b
