netdev - Re: [PATCH iproute2] netns: Fix an off-by-one strcpy() in netns_map

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Date:	Wed, 17 Feb 2016 17:55:09 -0800
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Nicolas Cavallari <nicolas.cavallari@...en-communications.fr>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] netns: Fix an off-by-one strcpy() in
 netns_map_add().

On Fri, 12 Feb 2016 14:47:39 +0100
Nicolas Cavallari <nicolas.cavallari@...en-communications.fr> wrote:

> netns_map_add() does a malloc of (sizeof (struct nsid_cache) +
> strlen(name)) and then proceed with strcpy() of name into the
> zero-length member at the end of the nsid_cache structure.  The
> nul-terminator is written outside of the allocated memory and may
> overwrite the allocator's internal structure.
> 
> This can trigger a segmentation fault on i386 uclibc with names of size 8:
> after the corruption occurs, the call to closedir() on netns_map_init()
> crashes while freeing the DIR structure.
> 
> Here is the relevant valgrind output:
> 
> ==1251== Memcheck, a memory error detector
> ==1251== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
> ==1251== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright
> info
> ==1251== Command: ./ip netns
> ==1251==
> ==1251== Invalid write of size 1
> ==1251==    at 0x4011975: strcpy (in
> /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
> ==1251==    by 0x8058B00: netns_map_add (ipnetns.c:181)
> ==1251==    by 0x8058E2A: netns_map_init (ipnetns.c:226)
> ==1251==    by 0x8058E79: do_netns (ipnetns.c:776)
> ==1251==    by 0x804D9FF: do_cmd (ip.c:110)
> ==1251==    by 0x804D814: main (ip.c:300)

Applied, thanks.