From 1a513170dd8f7a56dcabc879a2ce235131d99225 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 9 Nov 2015 17:51:23 -0800 Subject: [PATCH] net: fix a race in dst_release() commit d69bbf88c8d0b367cf3e3a052f6daadf630ee566 upstream. Only cpu seeing dst refcount going to 0 can safely dereference dst->flags. Otherwise an other cpu might already have freed the dst. Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst") Reported-by: Greg Thelen Signed-off-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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/dst.c b/net/core/dst.c index d5e2c4c09107..946e214787c6 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -272,7 +272,7 @@ void dst_release(struct dst_entry *dst) newrefcnt = atomic_dec_return(&dst->__refcnt); WARN_ON(newrefcnt < 0); - if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) { + if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) { dst = dst_destroy(dst); if (dst) __dst_free(dst); -- 2.30.2