netlabel: fix out-of-bounds memory accesses

BugLink: https://bugs.launchpad.net/bugs/1822271

[ Upstream commit 5578de48 ]

There are two array out-of-bounds memory accesses, one in
cipso_v4_map_lvl_valid(), the other in netlbl_bitmap_walk().  Both
errors are embarassingly simple, and the fixes are straightforward.

As a FYI for anyone backporting this patch to kernels prior to v4.8,
you'll want to apply the netlbl_bitmap_walk() patch to
cipso_v4_bitmap_walk() as netlbl_bitmap_walk() doesn't exist before
Linux v4.8.
Reported-by: Jann Horn <jannh@google.com>
Fixes: 446fda4f ("[NetLabel]: CIPSOv4 engine")
Fixes: 3faa8f98 ("netlabel: Move bitmap manipulation functions to the NetLabel core.")
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/ipv4/cipso_ipv4.c

@@ -167,7 +167,8 @@ static int cipso_v4_bitmap_walk(const unsigned char *bitmap,
 		    (state == 0 && (byte & bitmask) == 0))
 			return bit_spot;
 
-		bit_spot++;
+		if (++bit_spot >= bitmap_len)
+			return -1;
 		bitmask >>= 1;
 		if (bitmask == 0) {
 			byte = bitmap[++byte_offset];
@@ -737,7 +738,8 @@ static int cipso_v4_map_lvl_valid(const struct cipso_v4_doi *doi_def, u8 level)
 	case CIPSO_V4_MAP_PASS:
 		return 0;
 	case CIPSO_V4_MAP_TRANS:
-		if (doi_def->map.std->lvl.cipso[level] < CIPSO_V4_INV_LVL)
+		if ((level < doi_def->map.std->lvl.cipso_size) &&
+		    (doi_def->map.std->lvl.cipso[level] < CIPSO_V4_INV_LVL))
 			return 0;
 		break;
 	}