[NET]: Fix incorrect sg_mark_end() calls.

This fixes scatterlist corruptions added by

	commit 68e3f5dd4db62619fdbe520d36c9ebf62e672256
	[CRYPTO] users: Fix up scatterlist conversion errors

The issue is that the code calls sg_mark_end() which clobbers the
sg_page() pointer of the final scatterlist entry.

The first part fo the fix makes skb_to_sgvec() do __sg_mark_end().

After considering all skb_to_sgvec() call sites the most correct
solution is to call __sg_mark_end() in skb_to_sgvec() since that is
what all of the callers would end up doing anyways.

I suspect this might have fixed some problems in virtio_net which is
the sole non-crypto user of skb_to_sgvec().

Other similar sg_mark_end() cases were converted over to
__sg_mark_end() as well.

Arguably sg_mark_end() is a poorly named function because it doesn't
just "mark", it clears out the page pointer as a side effect, which is
what led to these bugs in the first place.

The one remaining plain sg_mark_end() call is in scsi_alloc_sgtable()
and arguably it could be converted to __sg_mark_end() if only so that
we can delete this confusing interface from linux/scatterlist.h

Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 37 insertions, 23 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 573e1724019..64b50ff7a41 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2028,8 +2028,8 @@ void __init skb_init(void)
  *      Fill the specified scatter-gather list with mappings/pointers into a
  *      region of the buffer space attached to a socket buffer.
  */
-int
-skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
+static int
+__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 {
         int start = skb_headlen(skb);
         int i, copy = start - offset;
@@ -2078,7 +2078,8 @@ skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
                         if ((copy = end - offset) > 0) {
                                 if (copy > len)
                                         copy = len;
-                                elt += skb_to_sgvec(list, sg+elt, offset - start, copy);
+                                elt += __skb_to_sgvec(list, sg+elt, offset - start,
+                                                      copy);
                                 if ((len -= copy) == 0)
                                         return elt;
                                 offset += copy;
@@ -2090,6 +2091,15 @@ skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
         return elt;
 }
 
+int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
+{
+        int nsg = __skb_to_sgvec(skb, sg, offset, len);
+
+        __sg_mark_end(&sg[nsg - 1]);
+
+        return nsg;
+}
+
 /**
  *      skb_cow_data - Check that a socket buffer's data buffers are writable
  *      @skb: The socket buffer to check.
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index cad4278025a..c31bccb9b52 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -111,9 +111,10 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
                                 goto unlock;
                 }
                 sg_init_table(sg, nfrags);
-                sg_mark_end(sg, skb_to_sgvec(skb, sg, esph->enc_data +
-                                                      esp->conf.ivlen -
-                                                      skb->data, clen));
+                skb_to_sgvec(skb, sg,
+                             esph->enc_data +
+                             esp->conf.ivlen -
+                             skb->data, clen);
                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
                 if (unlikely(sg != &esp->sgbuf[0]))
                         kfree(sg);
@@ -205,8 +206,9 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
                         goto out;
         }
         sg_init_table(sg, nfrags);
-        sg_mark_end(sg, skb_to_sgvec(skb, sg, sizeof(*esph) + esp->conf.ivlen,
-                                     elen));
+        skb_to_sgvec(skb, sg,
+                     sizeof(*esph) + esp->conf.ivlen,
+                     elen);
         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
         if (unlikely(sg != &esp->sgbuf[0]))
                 kfree(sg);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d3d8d5dfcee..eec02b29ffc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1083,7 +1083,7 @@ static int tcp_v4_do_calc_md5_hash(char *md5_hash, struct tcp_md5sig_key *key,
         sg_set_buf(&sg[block++], key->key, key->keylen);
         nbytes += key->keylen;
 
-        sg_mark_end(sg, block);
+        __sg_mark_end(&sg[block - 1]);
 
         /* Now store the Hash into the packet */
         err = crypto_hash_init(desc);
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ab17b5e6235..7db66f10e00 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -110,9 +110,10 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
                                 goto unlock;
                 }
                 sg_init_table(sg, nfrags);
-                sg_mark_end(sg, skb_to_sgvec(skb, sg, esph->enc_data +
-                                                      esp->conf.ivlen -
-                                                      skb->data, clen));
+                skb_to_sgvec(skb, sg,
+                             esph->enc_data +
+                             esp->conf.ivlen -
+                             skb->data, clen);
                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
                 if (unlikely(sg != &esp->sgbuf[0]))
                         kfree(sg);
@@ -209,9 +210,9 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
                         }
                 }
                 sg_init_table(sg, nfrags);
-                sg_mark_end(sg, skb_to_sgvec(skb, sg,
-                                             sizeof(*esph) + esp->conf.ivlen,
-                                             elen));
+                skb_to_sgvec(skb, sg,
+                             sizeof(*esph) + esp->conf.ivlen,
+                             elen);
                 ret = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
                 if (unlikely(sg != &esp->sgbuf[0]))
                         kfree(sg);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f1523b82cac..4b903288095 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -781,7 +781,7 @@ static int tcp_v6_do_calc_md5_hash(char *md5_hash, struct tcp_md5sig_key *key,
         sg_set_buf(&sg[block++], key->key, key->keylen);
         nbytes += key->keylen;
 
-        sg_mark_end(sg, block);
+        __sg_mark_end(&sg[block - 1]);
 
         /* Now store the hash into the packet */
         err = crypto_hash_init(desc);
diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index eebefb6ef13..c387cf68a08 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -237,7 +237,8 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
         len = data_size + call->conn->size_align - 1;
         len &= ~(call->conn->size_align - 1);
 
-        sg_init_table(sg, skb_to_sgvec(skb, sg, 0, len));
+        sg_init_table(sg, nsg);
+        skb_to_sgvec(skb, sg, 0, len);
         crypto_blkcipher_encrypt_iv(&desc, sg, sg, len);
 
         _leave(" = 0");
@@ -344,7 +345,7 @@ static int rxkad_verify_packet_auth(const struct rxrpc_call *call,
                 goto nomem;
 
         sg_init_table(sg, nsg);
-        sg_mark_end(sg, skb_to_sgvec(skb, sg, 0, 8));
+        skb_to_sgvec(skb, sg, 0, 8);
 
         /* start the decryption afresh */
         memset(&iv, 0, sizeof(iv));
@@ -426,7 +427,7 @@ static int rxkad_verify_packet_encrypt(const struct rxrpc_call *call,
         }
 
         sg_init_table(sg, nsg);
-        sg_mark_end(sg, skb_to_sgvec(skb, sg, 0, skb->len));
+        skb_to_sgvec(skb, sg, 0, skb->len);
 
         /* decrypt from the session key */
         payload = call->conn->key->payload.data;
@@ -701,7 +702,7 @@ static void rxkad_sg_set_buf2(struct scatterlist sg[2],
                 nsg++;
         }
 
-        sg_mark_end(sg, nsg);
+        __sg_mark_end(&sg[nsg - 1]);
 
         ASSERTCMP(sg[0].length + sg[1].length, ==, buflen);
 }
diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c
index 91cd8f0d1e1..ab7cbd6575c 100644
--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -211,8 +211,8 @@ encryptor(struct scatterlist *sg, void *data)
         if (thislen == 0)
                 return 0;
 
-        sg_mark_end(desc->infrags, desc->fragno);
-        sg_mark_end(desc->outfrags, desc->fragno);
+        __sg_mark_end(&desc->infrags[desc->fragno - 1]);
+        __sg_mark_end(&desc->outfrags[desc->fragno - 1]);
 
         ret = crypto_blkcipher_encrypt_iv(&desc->desc, desc->outfrags,
                                           desc->infrags, thislen);
@@ -293,7 +293,7 @@ decryptor(struct scatterlist *sg, void *data)
         if (thislen == 0)
                 return 0;
 
-        sg_mark_end(desc->frags, desc->fragno);
+        __sg_mark_end(&desc->frags[desc->fragno - 1]);
 
         ret = crypto_blkcipher_decrypt_iv(&desc->desc, desc->frags,
                                           desc->frags, thislen);