| From | Ben Hutchings <> | Date | Tue, 24 Nov 2015 22:33:59 +0000 | Subject | [PATCH 3.2 40/52] net: fix a race in dst_release() |
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3.2.74-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
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> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- 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);
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