crypto: algif_skcipher - only call put_page on referenced and used pages

For asynchronous operation, SGs are allocated without a page mapped to
them or with a page that is not used (ref-counted). If the SGL is freed,
the code must only call put_page for an SG if there was a page assigned
and ref-counted in the first place.

This fixes a kernel crash when using io_submit with more than one iocb
using the sendmsg and sendpage (vmsplice/splice) interface.

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

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 43839b00fe6c42fff5f8afbc04ffdff4e61a147d..903605dbc1a50282e8e3d7ced0bba148ec7ebe9c 100644 (file)
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -87,8 +87,13 @@ static void skcipher_free_async_sgls(struct skcipher_async_req *sreq)
        }
        sgl = sreq->tsg;
        n = sg_nents(sgl);
-       for_each_sg(sgl, sg, n, i)
-               put_page(sg_page(sg));
+       for_each_sg(sgl, sg, n, i) {
+               struct page *page = sg_page(sg);
+
+               /* some SGs may not have a page mapped */
+               if (page && page_ref_count(page))
+                       put_page(page);
+       }
 
        kfree(sreq->tsg);
 }