diff mbox series

[v7,6/8] fs, arm64: untag user address in copy_mount_options

Message ID c16db382982a7c2888e1241a455341118cd63b89.1538485901.git.andreyknvl@google.com (mailing list archive)
State New
Headers show
Series arm64: untag user pointers passed to the kernel | expand

Commit Message

Andrey Konovalov Oct. 2, 2018, 1:12 p.m. UTC 
In copy_mount_options a user address is being subtracted from TASK_SIZE.
If the address is lower than TASK_SIZE, the size is calculated to not
allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
However if the address is tagged, then the size will be calculated
incorrectly.

Untag the address before subtracting.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 fs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/fs/namespace.c b/fs/namespace.c
index 99186556f8d3..51f763fb9430 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2672,7 +2672,7 @@  void *copy_mount_options(const void __user * data)
 	 * the remainder of the page.
 	 */
 	/* copy_from_user cannot cross TASK_SIZE ! */
-	size = TASK_SIZE - (unsigned long)data;
+	size = TASK_SIZE - (unsigned long)untagged_addr(data);
 	if (size > PAGE_SIZE)
 		size = PAGE_SIZE;