Fix for buffer overflow in ldm_frag_add not sufficient

As Ben Hutchings discovered [1], the patch for CVE-2011-1017 (buffer
overflow in ldm_frag_add) is not sufficient.  The original patch in
commit c340b1d64000 ("fs/partitions/ldm.c: fix oops caused by corrupted
partition table") does not consider that, for subsequent fragments,
previously allocated memory is used.

[1] http://lkml.org/lkml/2011/5/6/407

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Timo Warns <warns@pre-sense.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/partitions/ldm.c b/fs/partitions/ldm.c
index ce4f62440425..a29d5ccf3d54 100644
--- a/fs/partitions/ldm.c
+++ b/fs/partitions/ldm.c
@@ -1335,6 +1335,11 @@ static bool ldm_frag_add (const u8 *data, int size, struct list_head *frags)
 
         list_add_tail (&f->list, frags);
 found:
+        if (rec >= f->num) {
+                ldm_error("REC value (%d) exceeds NUM value (%d)", rec, f->num);
+                return false;
+        }
+
         if (f->map & (1 << rec)) {
                 ldm_error ("Duplicate VBLK, part %d.", rec);
                 f->map &= 0x7F;                 /* Mark the group as broken */