fs/partitions/ldm.c: fix oops caused by corrupted partition table

The kernel automatically evaluates partition tables of storage devices.
The code for evaluating LDM partitions (in fs/partitions/ldm.c) contains
a bug that causes a kernel oops on certain corrupted LDM partitions.
A kernel subsystem seems to crash, because, after the oops, the kernel no
longer recognizes newly connected storage devices.

The patch validates the value of vblk_size.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Timo Warns <warns@pre-sense.de>
Cc: Eugene Teo <eugeneteo@kernel.sg>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Richard Russon <rich@flatcap.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 4 deletions

diff --git a/fs/partitions/ldm.c b/fs/partitions/ldm.c
index b10e3540d5b7..ce4f62440425 100644
--- a/fs/partitions/ldm.c
+++ b/fs/partitions/ldm.c
@@ -1299,6 +1299,11 @@ static bool ldm_frag_add (const u8 *data, int size, struct list_head *frags)
 
         BUG_ON (!data || !frags);
 
+        if (size < 2 * VBLK_SIZE_HEAD) {
+                ldm_error("Value of size is to small.");
+                return false;
+        }
+
         group = get_unaligned_be32(data + 0x08);
         rec   = get_unaligned_be16(data + 0x0C);
         num   = get_unaligned_be16(data + 0x0E);
@@ -1306,6 +1311,10 @@ static bool ldm_frag_add (const u8 *data, int size, struct list_head *frags)
                 ldm_error ("A VBLK claims to have %d parts.", num);
                 return false;
         }
+        if (rec >= num) {
+                ldm_error("REC value (%d) exceeds NUM value (%d)", rec, num);
+                return false;
+        }
 
         list_for_each (item, frags) {
                 f = list_entry (item, struct frag, list);
@@ -1334,10 +1343,9 @@ found:
 
         f->map |= (1 << rec);
 
-        if (num > 0) {
-                data += VBLK_SIZE_HEAD;
-                size -= VBLK_SIZE_HEAD;
-        }
+        data += VBLK_SIZE_HEAD;
+        size -= VBLK_SIZE_HEAD;
+
         memcpy (f->data+rec*(size-VBLK_SIZE_HEAD)+VBLK_SIZE_HEAD, data, size);
 
         return true;