Hi:
Just noticed that algif_skcipher fails to apply the sk_sndbuf limit
correctly unless it is a multiple of PAGE_SIZE. What happens is
that the merge path will exceed sk_sndbuf causing the subsequent
limit comparison to fail as it tries to do an unsigned comparison
with a negative value.
This patch fixes the problem.
commit 0f6bb83cb12e4617e696ffa566f3fc6c092686e2
Author: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Tue Nov 30 16:49:02 2010 +0800
crypto: algif_skcipher - Fixed overflow when sndbuf is page aligned
When sk_sndbuf is not a multiple of PAGE_SIZE, the limit tests
in sendmsg fail as the limit variable becomes negative and we're
using an unsigned comparison.
The same thing can happen if sk_sndbuf is lowered after a sendmsg
call.
This patch fixes this by always taking the signed maximum of limit
and 0 before we perform the comparison.
It also rounds the value of sk_sndbuf down to a multiple of PAGE_SIZE
so that we don't end up allocating a page only to use a small number
of bytes in it because we're bound by sk_sndbuf.
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 9b2f440..1f33480 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -52,12 +52,18 @@ struct skcipher_ctx {
#define MAX_SGL_ENTS ((PAGE_SIZE - sizeof(struct skcipher_sg_list)) / \
sizeof(struct scatterlist) - 1)
-static inline bool skcipher_writable(struct sock *sk)
+static inline int skcipher_sndbuf(struct sock *sk)
{
struct alg_sock *ask = alg_sk(sk);
struct skcipher_ctx *ctx = ask->private;
- return ctx->used + PAGE_SIZE <= max_t(int, sk->sk_sndbuf, PAGE_SIZE);
+ return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
+ ctx->used, 0);
+}
+
+static inline bool skcipher_writable(struct sock *sk)
+{
+ return PAGE_SIZE <= skcipher_sndbuf(sk);
}
static int skcipher_alloc_sgl(struct sock *sk)
@@ -245,7 +251,6 @@ static int skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
struct af_alg_control con = {};
long copied = 0;
bool enc = 0;
- int limit;
int err;
int i;
@@ -281,9 +286,6 @@ static int skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
memcpy(ctx->iv, con.iv->iv, ivsize);
}
- limit = max_t(int, sk->sk_sndbuf, PAGE_SIZE);
- limit -= ctx->used;
-
while (size) {
struct scatterlist *sg;
unsigned long len = size;
@@ -309,20 +311,16 @@ static int skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
ctx->used += len;
copied += len;
size -= len;
- limit -= len;
continue;
}
- if (limit < PAGE_SIZE) {
+ if (!skcipher_writable(sk)) {
err = skcipher_wait_for_wmem(sk, msg->msg_flags);
if (err)
goto unlock;
-
- limit = max_t(int, sk->sk_sndbuf, PAGE_SIZE);
- limit -= ctx->used;
}
- len = min_t(unsigned long, len, limit);
+ len = min_t(unsigned long, len, skcipher_sndbuf(sk));
err = skcipher_alloc_sgl(sk);
if (err)
@@ -352,7 +350,6 @@ static int skcipher_sendmsg(struct kiocb *unused, struct socket *sock,
ctx->used += plen;
copied += plen;
size -= plen;
- limit -= plen;
sgl->cur++;
} while (len && sgl->cur < MAX_SGL_ENTS);
@@ -380,7 +377,6 @@ static ssize_t skcipher_sendpage(struct socket *sock, struct page *page,
struct skcipher_ctx *ctx = ask->private;
struct skcipher_sg_list *sgl;
int err = -EINVAL;
- int limit;
lock_sock(sk);
if (!ctx->more && ctx->used)
@@ -389,16 +385,10 @@ static ssize_t skcipher_sendpage(struct socket *sock, struct page *page,
if (!size)
goto done;
- limit = max_t(int, sk->sk_sndbuf, PAGE_SIZE);
- limit -= ctx->used;
-
- if (limit < PAGE_SIZE) {
+ if (!skcipher_writable(sk)) {
err = skcipher_wait_for_wmem(sk, flags);
if (err)
goto unlock;
-
- limit = max_t(int, sk->sk_sndbuf, PAGE_SIZE);
- limit -= ctx->used;
}
err = skcipher_alloc_sgl(sk);
Cheers,
--
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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