Re: [PATCH net] igmp: fix memory leak in igmpv3_del_delrec()

[David Miller <davem@davemloft.net>]

From: Eric Dumazet <edumazet@google.com>
Date: Thu, 27 Jun 2019 01:27:01 -0700

> im->tomb and/or im->sources might not be NULL, but we
> currently overwrite their values blindly.
> 
> Using swap() will make sure the following call to kfree_pmc(pmc)
> will properly free the psf structures.
> 
> Tested with the C repro provided by syzbot, which basically does :
> 
>  socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
>  setsockopt(3, SOL_IP, IP_ADD_MEMBERSHIP, "\340\0\0\2\177\0\0\1\0\0\0\0", 12) = 0
>  ioctl(3, SIOCSIFFLAGS, {ifr_name="lo", ifr_flags=0}) = 0
>  setsockopt(3, SOL_IP, IP_MSFILTER, "\340\0\0\2\177\0\0\1\1\0\0\0\1\0\0\0\377\377\377\377", 20) = 0
>  ioctl(3, SIOCSIFFLAGS, {ifr_name="lo", ifr_flags=IFF_UP}) = 0
>  exit_group(0)                    = ?
> 
> BUG: memory leak
> unreferenced object 0xffff88811450f140 (size 64):
 ...
> Fixes: 24803f38a5c0 ("igmp: do not remove igmp souce list info when set link down")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Hangbin Liu <liuhangbin@gmail.com>
> Reported-by: syzbot+6ca1abd0db68b5173a4f@syzkaller.appspotmail.com

Applied and queued up for -stable, thanks.