[PATCH 3.16 134/366] UBIFS: Fix potential integer overflow in allocation

[Ben Hutchings]

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Silvio Cesare <silvio.cesare@xxxxxxxxx>

commit 353748a359f1821ee934afc579cf04572406b420 upstream.

There is potential for the size and len fields in ubifs_data_node to be
too large causing either a negative value for the length fields or an
integer overflow leading to an incorrect memory allocation. Likewise,
when the len field is small, an integer underflow may occur.

Signed-off-by: Silvio Cesare <silvio.cesare@xxxxxxxxx>
Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
[bwh: Backported to 3.16: We have a different set of length variables in
 recomp_data_node()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/ubifs/journal.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -1099,10 +1099,11 @@ out_free:
 static int recomp_data_node(struct ubifs_data_node *dn, int *new_len)
 {
 	void *buf;
-	int err, len, compr_type, out_len;
+	int err, compr_type;
+	u32 len, out_len;
 
 	out_len = le32_to_cpu(dn->size);
-	buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS);
+	buf = kmalloc_array(out_len, WORST_COMPR_FACTOR, GFP_NOFS);
 	if (!buf)
 		return -ENOMEM;