From: Daniel Borkmann Date: Sat, 7 Sep 2013 13:13:20 +0000 (+0200) Subject: net: fib: fib6_add: fix potential NULL pointer dereference X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ae7b4e1f213aa659aedf9c6ecad0bf5f0476e1e2;p=linux-beck.git net: fib: fib6_add: fix potential NULL pointer dereference When the kernel is compiled with CONFIG_IPV6_SUBTREES, and we return with an error in fn = fib6_add_1(), then error codes are encoded into the return pointer e.g. ERR_PTR(-ENOENT). In such an error case, we write the error code into err and jump to out, hence enter the if(err) condition. Now, if CONFIG_IPV6_SUBTREES is enabled, we check for: if (pn != fn && pn->leaf == rt) ... if (pn != fn && !pn->leaf && !(pn->fn_flags & RTN_RTINFO)) ... Since pn is NULL and fn is f.e. ERR_PTR(-ENOENT), then pn != fn evaluates to true and causes a NULL-pointer dereference on further checks on pn. Fix it, by setting both NULL in error case, so that pn != fn already evaluates to false and no further dereference takes place. This was first correctly implemented in 4a287eba2 ("IPv6 routing, NLM_F_* flag support: REPLACE and EXCL flags support, warn about missing CREATE flag"), but the bug got later on introduced by 188c517a0 ("ipv6: return errno pointers consistently for fib6_add_1()"). Signed-off-by: Daniel Borkmann Cc: Lin Ming Cc: Matti Vaittinen Cc: Hannes Frederic Sowa Acked-by: Hannes Frederic Sowa Acked-by: Matti Vaittinen Signed-off-by: David S. Miller --- diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 73db48eba1c4..5bec666aba61 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -825,9 +825,9 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info) fn = fib6_add_1(root, &rt->rt6i_dst.addr, rt->rt6i_dst.plen, offsetof(struct rt6_info, rt6i_dst), allow_create, replace_required); - if (IS_ERR(fn)) { err = PTR_ERR(fn); + fn = NULL; goto out; }