crypto: algif_skcipher - Fixed blocking recvmsg

As most (all?) users of algif_skcipher are single-threaded and
therefore always write before reading from an algif_skcipher
socket, they never block and exercise that code-path.

It turns out that code path doesn't even work because we never
reload ctx->used after waking up so we never even see the new
data and immediately return an error (and a loud WARN_ON).

This patch fixes this by always reloading ctx->used.

Reported-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Stephan Mueller <smueller@chronox.de>

1 files changed, 2 insertions, 3 deletions

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 34389964000d..f80e652ef0d0 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -448,14 +448,13 @@ static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock,
                         while (!sg->length)
                                 sg++;
 
-                        used = ctx->used;
-                        if (!used) {
+                        if (!ctx->used) {
                                 err = skcipher_wait_for_data(sk, flags);
                                 if (err)
                                         goto unlock;
                         }
 
-                        used = min_t(unsigned long, used, seglen);
+                        used = min_t(unsigned long, ctx->used, seglen);
 
                         used = af_alg_make_sg(&ctx->rsgl, from, used, 1);
                         err = used;