linux-kernel - [PATCH 3.16 22/55] net: filter: fix possible use after free

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Date:	Mon, 13 Oct 2014 04:24:36 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Borkmann <dborkman@...hat.com>
Subject: [PATCH 3.16 22/55] net: filter: fix possible use after free

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

[ No appicable upstream commit, this bug has been subsequently been
  fixed as a side effect of other changes. ]

If kmemdup() fails, we free fp->orig_prog and return -ENOMEM

sk_attach_filter()
 -> sk_filter_uncharge(sk, fp)
  -> sk_filter_release(fp)
   -> call_rcu(&fp->rcu, sk_filter_release_rcu)
    -> sk_filter_release_rcu()
     -> sk_release_orig_filter()
        fprog = fp->orig_prog; // not NULL, but points to freed memory
	  kfree(fprog->filter); // use after free, potential corruption
          kfree(fprog); // double free or corruption

Note: This was fixed in 3.17+ with commit 278571baca2a
("net: filter: simplify socket charging")

Found by AddressSanitizer

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Fixes: a3ea269b8bcdb ("net: filter: keep original BPF program around")
Acked-by: Alexei Starovoitov <ast@...mgrid.com>
Acked-by: Daniel Borkmann <dborkman@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/filter.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1318,6 +1318,7 @@ static int sk_store_orig_filter(struct s
 	fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
 	if (!fkprog->filter) {
 		kfree(fp->orig_prog);
+		fp->orig_prog = NULL;
 		return -ENOMEM;
 	}
 


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