From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sat, 16 Apr 2005 22:24:10 +0000 (-0700)
Subject: [PATCH] Fix dst_destroy() race
X-Git-Tag: v2.6.12-rc3~223
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=6775cab98b89b2caa10dce4b07e2c81999e45517;p=~emulex%2Finfiniband.git

[PATCH] Fix dst_destroy() race

When we are not the real parent of the dst (e.g., when we're xfrm_dst and
the child is an rtentry), it may already be on the GC list.

In fact the current code is buggy to, we need to check dst->flags before
the dec as dst may no longer be valid afterwards.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/net/core/dst.c b/net/core/dst.c
index 3bf6cc43481..fc434ade527 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -198,13 +198,15 @@ again:
 
 	dst = child;
 	if (dst) {
+		int nohash = dst->flags & DST_NOHASH;
+
 		if (atomic_dec_and_test(&dst->__refcnt)) {
 			/* We were real parent of this dst, so kill child. */
-			if (dst->flags&DST_NOHASH)
+			if (nohash)
 				goto again;
 		} else {
 			/* Child is still referenced, return it for freeing. */
-			if (dst->flags&DST_NOHASH)
+			if (nohash)
 				return dst;
 			/* Child is still in his hash table */
 		}