crypto: af_alg - Set merge to zero early in af_alg_sendmsg

If an error causes af_alg_sendmsg to abort, ctx->merge may contain
a garbage value from the previous loop.  This may then trigger a
crash on the next entry into af_alg_sendmsg when it attempts to do
a merge that can't be done.

Fix this by setting ctx->merge to zero near the start of the loop.

Fixes: 8ff590903d5 ("crypto: algif_skcipher - User-space interface for skcipher operations")
Reported-by: Muhammad Alifa Ramdhan <ramdhan@starlabs.sg>
Reported-by: Bing-Jhong Billy Jheng <billy@starlabs.sg>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 0da7c1ac778a0ed61d6dbb388f07a78b154f936b..407f2c238f2c67101350380d5f019a476a7e79d0 100644 (file)
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1019,6 +1019,8 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
                        continue;
                }
 
+               ctx->merge = 0;
+
                if (!af_alg_writable(sk)) {
                        err = af_alg_wait_for_wmem(sk, msg->msg_flags);
                        if (err)
@@ -1058,7 +1060,6 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
                        ctx->used += plen;
                        copied += plen;
                        size -= plen;
-                       ctx->merge = 0;
                } else {
                        do {
                                struct page *pg;