[Lucid, Maverick, Natty] [CVE-2011-1017] [PATCH 1/1] fs/partitions/ldm.c: fix oops caused by corrupted partition table, CVE-2011-1017

[Brad Figg]

From: Timo Warns <Warns at pre-sense.de>

BugLink: http://bugs.launchpad.net/bugs/771382

CVE-2011-1017

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

(cherry-pick from commit c340b1d640001c8c9ecff74f68fd90422ae2448a)
Signed-off-by: Brad Figg <brad.figg at canonical.com>
---
 fs/partitions/ldm.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/partitions/ldm.c b/fs/partitions/ldm.c
index b10e354..ce4f624 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;
-- 
1.7.0.4