| Date | Sun, 17 Jan 2016 19:49:32 -0800 | Subject | Re: [PATCH 3.2 42/70] net: possible use after free in dst_release | From | Francesco Ruggeri <> |
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On Sun, Jan 17, 2016 at 7:18 PM, Ben Hutchings <ben@decadent.org.uk> wrote: > 3.2.76-rc1 review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Francesco Ruggeri <fruggeri@aristanetworks.com> > > 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 <fruggeri@arista.com> > Acked-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 | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > --- 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;
Only one minor thing. Before 3.6 dst->flags was an int.
Thanks, Francesco
> > 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); >
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