Re: [PATCH net] net: ipvs: avoid stat macros calls from preemptible context

[Simon Horman]

On Mon, Jan 15, 2024 at 05:39:22PM +0300, Fedor Pchelkin wrote:
> Inside decrement_ttl() upon discovering that the packet ttl has exceeded,
> __IP_INC_STATS and __IP6_INC_STATS macros can be called from preemptible
> context having the following backtrace:
> 
> check_preemption_disabled: 48 callbacks suppressed
> BUG: using __this_cpu_add() in preemptible [00000000] code: curl/1177
> caller is decrement_ttl+0x217/0x830
> CPU: 5 PID: 1177 Comm: curl Not tainted 6.7.0+ #34
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 04/01/2014
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0xbd/0xe0
>  check_preemption_disabled+0xd1/0xe0
>  decrement_ttl+0x217/0x830
>  __ip_vs_get_out_rt+0x4e0/0x1ef0
>  ip_vs_nat_xmit+0x205/0xcd0
>  ip_vs_in_hook+0x9b1/0x26a0
>  nf_hook_slow+0xc2/0x210
>  nf_hook+0x1fb/0x770
>  __ip_local_out+0x33b/0x640
>  ip_local_out+0x2a/0x490
>  __ip_queue_xmit+0x990/0x1d10
>  __tcp_transmit_skb+0x288b/0x3d10
>  tcp_connect+0x3466/0x5180
>  tcp_v4_connect+0x1535/0x1bb0
>  __inet_stream_connect+0x40d/0x1040
>  inet_stream_connect+0x57/0xa0
>  __sys_connect_file+0x162/0x1a0
>  __sys_connect+0x137/0x160
>  __x64_sys_connect+0x72/0xb0
>  do_syscall_64+0x6f/0x140
>  entry_SYSCALL_64_after_hwframe+0x6e/0x76
> RIP: 0033:0x7fe6dbbc34e0
> 
> Use the corresponding preemption-aware variants: IP_INC_STATS and
> IP6_INC_STATS.
> 
> Found by Linux Verification Center (linuxtesting.org).
> 
> Fixes: 8d8e20e2d7bb ("ipvs: Decrement ttl")
> Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>

Acked-by: Simon Horman <horms@xxxxxxxxxx>