| From d69bbf88c8d0b367cf3e3a052f6daadf630ee566 Mon Sep 17 00:00:00 2001 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Mon, 9 Nov 2015 17:51:23 -0800 |
| Subject: 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 <gthelen@google.com> |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| [lizf: Backported to 3.4: adjust context] |
| Signed-off-by: Zefan Li <lizefan@huawei.com> |
| --- |
| net/core/dst.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- 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); |