Re: [RFC] igmp: address pmc kmemleak from on igmpv3_del_delrec()

[Cong Wang <xiyou.wangcong@gmail.com>]

On Fri, Feb 3, 2017 at 1:20 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> When we igmpv3_add_delrec() we kzalloc the pmc, but when users
> call    igmpv3_del_delrec() we never free the pmc. This was caught
> by the following kmemleak splat:
>
> unreferenced object 0xffff99666ff43b40 (size 192):
>   comm "systemd-resolve", pid 1258, jiffies 4309905600 (age 2138.352s)
>   hex dump (first 32 bytes):
>     00 6a 64 72 66 99 ff ff e0 00 00 fc 00 00 00 00  .jdrf...........
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffffb3a5f7ea>] kmemleak_alloc+0x4a/0xa0
>     [<ffffffffb36044e7>] kmem_cache_alloc_trace+0x107/0x240
>     [<ffffffffb39ddbed>] igmp_group_dropped+0xfd/0x270
>     [<ffffffffb39de5cf>] ip_mc_dec_group+0xaf/0x110
>     [<ffffffffb39de6e6>] ip_mc_leave_group+0xb6/0x140
>     [<ffffffffb39a55d7>] do_ip_setsockopt.isra.13+0x4c7/0xed0
>     [<ffffffffb39a6014>] ip_setsockopt+0x34/0xb0
>     [<ffffffffb39ced9b>] udp_setsockopt+0x1b/0x30
>     [<ffffffffb393f064>] sock_common_setsockopt+0x14/0x20
>     [<ffffffffb393dd10>] SyS_setsockopt+0x80/0xe0
>     [<ffffffffb3403b4b>] do_syscall_64+0x5b/0xc0
>     [<ffffffffb3a6b3af>] return_from_SYSCALL_64+0x0/0x6a
>     [<ffffffffffffffff>] 0xffffffffffffffff
>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
>
> I can reproduce this over time on a qemu box running next-20170125.
> After running this for a while I no longer see the splat. This needs
> confirmation form folks more familiar with the code, hence RFC. If
> this is a real fix we need appropriate tags for the patch.


Looks good to me. Adding some people who recent touched it to CC.

>
>  net/ipv4/igmp.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 5b15459955f8..44fd86de2823 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -1172,6 +1172,7 @@ static void igmpv3_del_delrec(struct in_device *in_dev, struct ip_mc_list *im)
>                                 psf->sf_crcount = im->crcount;
>                 }
>                 in_dev_put(pmc->interface);
> +               kfree(pmc);
>         }
>         spin_unlock_bh(&im->lock);
>  }
> --
> 2.11.0
>