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Message-Id: <20170425150419.2060-1-Jason@zx2c4.com>
Date: Tue, 25 Apr 2017 17:04:19 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
davem@...emloft.net,
David.Laight@...lab.com,
kernel-hardening@...ts.openwall.com
Cc: "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow
This is a defense-in-depth measure in response to bugs like
4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec")
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
v4 fixes the commit message and moves the check into the inner-most if.
net/core/skbuff.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f86bf69cfb8d..e75640006d78 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3489,7 +3489,9 @@ void __init skb_init(void)
* @len: Length of buffer space to be mapped
*
* Fill the specified scatter-gather list with mappings/pointers into a
- * region of the buffer space attached to a socket buffer.
+ * region of the buffer space attached to a socket buffer. Returns either
+ * the number of scatterlist items used, or -EMSGSIZE if the contents
+ * could not fit.
*/
static int
__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
@@ -3517,6 +3519,8 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]);
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ if (elt && sg_is_last(&sg[elt - 1]))
+ return -EMSGSIZE;
if (copy > len)
copy = len;
@@ -3537,6 +3541,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
end = start + frag_iter->len;
if ((copy = end - offset) > 0) {
+ if (elt && sg_is_last(&sg[elt - 1]))
+ return -EMSGSIZE;
+
if (copy > len)
copy = len;
elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start,
@@ -3581,6 +3588,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le
{
int nsg = __skb_to_sgvec(skb, sg, offset, len);
+ if (nsg <= 0)
+ return nsg;
+
sg_mark_end(&sg[nsg - 1]);
return nsg;
--
2.12.2
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