From ccf8b3948a05d0ac28fecfefde3ec9e75d43a1bd Mon Sep 17 00:00:00 2001 From: Francesco Ruggeri Date: Wed, 6 Jan 2016 00:18:48 -0800 Subject: [PATCH] net: possible use after free in dst_release commit 07a5d38453599052aff0877b16bb9c1585f08609 upstream. dst_release should not access dst->flags after decrementing __refcnt to 0. The dst_entry may be in dst_busy_list and dst_gc_task may dst_destroy it before dst_release gets a chance to access dst->flags. Fixes: d69bbf88c8d0 ("net: fix a race in dst_release()") Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst") Signed-off-by: Francesco Ruggeri Acked-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- net/core/dst.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/dst.c b/net/core/dst.c index 946e214787c6..59381decf0aa 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -269,10 +269,11 @@ void dst_release(struct dst_entry *dst) { if (dst) { int newrefcnt; + unsigned short nocache = dst->flags & DST_NOCACHE; newrefcnt = atomic_dec_return(&dst->__refcnt); WARN_ON(newrefcnt < 0); - if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) { + if (!newrefcnt && unlikely(nocache)) { dst = dst_destroy(dst); if (dst) __dst_free(dst); -- 2.39.2