crypto: af_alg - get_page upon reassignment to TX SGL

When a page is assigned to a TX SGL, call get_page to increment the
reference counter. It is possible that one page is referenced in
multiple SGLs:

- in the global TX SGL in case a previous af_alg_pull_tsgl only
reassigned parts of a page to a per-request TX SGL

- in the per-request TX SGL as assigned by af_alg_pull_tsgl

Note, multiple requests can be active at the same time whose TX SGLs all
point to different parts of the same page.

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

1 files changed, 2 insertions, 4 deletions

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index d6936c0e08d9..ffa9f4ccd9b4 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -641,9 +641,9 @@ void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
                                 if (dst_offset >= plen) {
                                         /* discard page before offset */
                                         dst_offset -= plen;
-                                        put_page(page);
                                 } else {
                                         /* reassign page to dst after offset */
+                                        get_page(page);
                                         sg_set_page(dst + j, page,
                                                     plen - dst_offset,
                                                     sg[i].offset + dst_offset);
@@ -661,9 +661,7 @@ void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
                         if (sg[i].length)
                                 return;
 
-                        if (!dst)
-                                put_page(page);
-
+                        put_page(page);
                         sg_assign_page(sg + i, NULL);
                 }