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

commit 445a582738de6802669aeed9c33ca406c23c3b1f upstream.

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.

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

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index f5e9f9310b4864929e6aa542011c69d038df20e1..b3b0004ea8ac9986e13ca1a7a5e5a517804d85e7 100644 (file)
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -86,8 +86,13 @@ 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 && atomic_read(&page->_count))
+                       put_page(page);
+       }
 
        kfree(sreq->tsg);
 }