netdev - Re: [PATCH net] net: skb_segment() should not return NULL

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Date:   Sat, 21 Jul 2018 19:35:08 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        alexander.h.duyck@...el.com
Subject: Re: [PATCH net] net: skb_segment() should not return NULL

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 19 Jul 2018 16:04:38 -0700

> syzbot caught a NULL deref [1], caused by skb_segment()
> 
> skb_segment() has many "goto err;" that assume the @err variable
> contains -ENOMEM.
> 
> A successful call to __skb_linearize() should not clear @err,
> otherwise a subsequent memory allocation error could return NULL.

Ugh, good catch.

> While we are at it, we might use -EINVAL instead of -ENOMEM when
> MAX_SKB_FRAGS limit is reached.
 ...
> Fixes: ddff00d42043 ("net: Move skb_has_shared_frag check out of GRE code and into segmentation")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Alexander Duyck <alexander.h.duyck@...el.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable.