Commit ccaffff1 authored Aug 09, 2017 by Willem de Bruijn Committed by David S. Miller Aug 09, 2017

sock: fix zerocopy panic in mem accounting



Only call mm_unaccount_pinned_pages when releasing a struct ubuf_info
that has initialized its field uarg->mmp.

Before this patch, a vhost-net with experimental_zcopytx can crash in

  mm_unaccount_pinned_pages
  sock_zerocopy_put
  skb_zcopy_clear
  skb_release_data

Only sock_zerocopy_alloc initializes this field. Move the unaccount
call from generic sock_zerocopy_put to its specific callback
sock_zerocopy_callback.

Fixes: a91dbff5 ("sock: ulimit on MSG_ZEROCOPY pages")
Reported-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent d5e7f827

net/core/skbuff.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1044,6 +1044,8 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
		u32 lo, hi;
		u16 len;

		mm_unaccount_pinned_pages(&uarg->mmp);

		/* if !len, there was only 1 call, and it was aborted
		* so do not queue a completion notification
		*/
		@@ -1084,8 +1086,6 @@ EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
		void sock_zerocopy_put(struct ubuf_info *uarg)
		{
		if (uarg && atomic_dec_and_test(&uarg->refcnt)) {
		mm_unaccount_pinned_pages(&uarg->mmp);

		if (uarg->callback)
		uarg->callback(uarg, uarg->zerocopy);
		else

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