[PATCH 3.13 2/3] floppy: ignore kernel-only members in FDRAWCMD ioctl input

[Kamal Mostafa <kamal@canonical.com>]

3.13.11.1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Daley <mattd@bugfuzz.com>

commit ef87dbe7614341c2e7bfe8d32fcb7028cc97442c upstream.

Always clear out these floppy_raw_cmd struct members after copying the
entire structure from userspace so that the in-kernel version is always
valid and never left in an interdeterminate state.

Signed-off-by: Matthew Daley <mattd@bugfuzz.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
References: CVE-2014-1737
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/block/floppy.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 000abe2..10fbd3f 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3107,10 +3107,11 @@ loop:
 		return -ENOMEM;
 	*rcmd = ptr;
 	ret = copy_from_user(ptr, param, sizeof(*ptr));
-	if (ret)
-		return -EFAULT;
 	ptr->next = NULL;
 	ptr->buffer_length = 0;
+	ptr->kernel_data = NULL;
+	if (ret)
+		return -EFAULT;
 	param += sizeof(struct floppy_raw_cmd);
 	if (ptr->cmd_count > 33)
 			/* the command may now also take up the space
@@ -3126,7 +3127,6 @@ loop:
 	for (i = 0; i < 16; i++)
 		ptr->reply[i] = 0;
 	ptr->resultcode = 0;
-	ptr->kernel_data = NULL;
 
 	if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
 		if (ptr->length <= 0)
-- 
1.9.1