FAILED: patch "[PATCH] dm verity: fix crash on bufio buffer that was allocated with" failed to apply to 4.14-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From e4b069e0945fa14c71cf8b5b89f8b1b2aa68dbc2 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 22 Aug 2018 12:45:51 -0400
Subject: [PATCH] dm verity: fix crash on bufio buffer that was allocated with
 vmalloc

Since commit d1ac3ff008fb ("dm verity: switch to using asynchronous hash
crypto API") dm-verity uses asynchronous crypto calls for verification,
so that it can use hardware with asynchronous processing of crypto
operations.

These asynchronous calls don't support vmalloc memory, but the buffer data
can be allocated with vmalloc if dm-bufio is short of memory and uses a
reserved buffer that was preallocated in dm_bufio_client_create().

Fix verity_hash_update() so that it deals with vmalloc'd memory
correctly.

Reported-by: "Xiao, Jin" <jin.xiao@intel.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: d1ac3ff008fb ("dm verity: switch to using asynchronous hash crypto API")
Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 12decdbd722d..fc65f0dedf7f 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -99,10 +99,26 @@ static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
 {
 	struct scatterlist sg;
 
-	sg_init_one(&sg, data, len);
-	ahash_request_set_crypt(req, &sg, NULL, len);
-
-	return crypto_wait_req(crypto_ahash_update(req), wait);
+	if (likely(!is_vmalloc_addr(data))) {
+		sg_init_one(&sg, data, len);
+		ahash_request_set_crypt(req, &sg, NULL, len);
+		return crypto_wait_req(crypto_ahash_update(req), wait);
+	} else {
+		do {
+			int r;
+			size_t this_step = min_t(size_t, len, PAGE_SIZE - offset_in_page(data));
+			flush_kernel_vmap_range((void *)data, this_step);
+			sg_init_table(&sg, 1);
+			sg_set_page(&sg, vmalloc_to_page(data), this_step, offset_in_page(data));
+			ahash_request_set_crypt(req, &sg, NULL, this_step);
+			r = crypto_wait_req(crypto_ahash_update(req), wait);
+			if (unlikely(r))
+				return r;
+			data += this_step;
+			len -= this_step;
+		} while (len);
+		return 0;
+	}
 }
 
 /*