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: <[email protected]> Signed-off-by: Stephan Mueller <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
berg · Aug 22, 2017 · 445a582 · 445a582
1 parent 549f641
commit 445a582
Showing 1 changed file with 7 additions and 2 deletions.
diff --git 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);
 }