[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>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index eebefb6e..c387cf6 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);
 }