netlabel: fix a problem when setting bits below the previously lowest bit

The NetLabel category (catmap) functions have a problem in that they
assume categories will be set in an increasing manner, e.g. the next
category set will always be larger than the last.  Unfortunately, this
is not a valid assumption and could result in problems when attempting
to set categories less than the startbit in the lowest catmap node.
In some cases kernel panics and other nasties can result.

This patch corrects the problem by checking for this and allocating a
new catmap node instance and placing it at the front of the list.

Cc: stable@vger.kernel.org
Reported-by: Christian Evans <frodox@zoho.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Tested-by: Casey Schaufler <casey@schaufler-ca.com>

1 files changed, 18 insertions, 8 deletions

diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c
index 3045a964f39c..84e810bef39a 100644
--- a/net/netlabel/netlabel_kapi.c
+++ b/net/netlabel/netlabel_kapi.c
@@ -522,7 +522,7 @@ int netlbl_secattr_catmap_walk_rng(struct netlbl_lsm_secattr_catmap *catmap,
 
 /**
  * netlbl_secattr_catmap_setbit - Set a bit in a LSM secattr catmap
- * @catmap: the category bitmap
+ * @catmap: pointer to the category bitmap
  * @bit: the bit to set
  * @flags: memory allocation flags
  *
@@ -531,18 +531,25 @@ int netlbl_secattr_catmap_walk_rng(struct netlbl_lsm_secattr_catmap *catmap,
  * negative values on failure.
  *
  */
-int netlbl_secattr_catmap_setbit(struct netlbl_lsm_secattr_catmap *catmap,
+int netlbl_secattr_catmap_setbit(struct netlbl_lsm_secattr_catmap **catmap,
 				 u32 bit,
 				 gfp_t flags)
 {
-	struct netlbl_lsm_secattr_catmap *iter = catmap;
+	struct netlbl_lsm_secattr_catmap *iter = *catmap;
 	u32 node_bit;
 	u32 node_idx;
 
 	while (iter->next != NULL &&
 	       bit >= (iter->startbit + NETLBL_CATMAP_SIZE))
 		iter = iter->next;
-	if (bit >= (iter->startbit + NETLBL_CATMAP_SIZE)) {
+	if (bit < iter->startbit) {
+		iter = netlbl_secattr_catmap_alloc(flags);
+		if (iter == NULL)
+			return -ENOMEM;
+		iter->next = *catmap;
+		iter->startbit = bit & ~(NETLBL_CATMAP_SIZE - 1);
+		*catmap = iter;
+	} else if (bit >= (iter->startbit + NETLBL_CATMAP_SIZE)) {
 		iter->next = netlbl_secattr_catmap_alloc(flags);
 		if (iter->next == NULL)
 			return -ENOMEM;
@@ -560,7 +567,7 @@ int netlbl_secattr_catmap_setbit(struct netlbl_lsm_secattr_catmap *catmap,
 
 /**
  * netlbl_secattr_catmap_setrng - Set a range of bits in a LSM secattr catmap
- * @catmap: the category bitmap
+ * @catmap: pointer to the category bitmap
  * @start: the starting bit
  * @end: the last bit in the string
  * @flags: memory allocation flags
@@ -570,15 +577,16 @@ int netlbl_secattr_catmap_setbit(struct netlbl_lsm_secattr_catmap *catmap,
  * on success, negative values on failure.
  *
  */
-int netlbl_secattr_catmap_setrng(struct netlbl_lsm_secattr_catmap *catmap,
+int netlbl_secattr_catmap_setrng(struct netlbl_lsm_secattr_catmap **catmap,
 				 u32 start,
 				 u32 end,
 				 gfp_t flags)
 {
 	int ret_val = 0;
-	struct netlbl_lsm_secattr_catmap *iter = catmap;
+	struct netlbl_lsm_secattr_catmap *iter = *catmap;
 	u32 iter_max_spot;
 	u32 spot;
+	u32 orig_spot = iter->startbit;
 
 	/* XXX - This could probably be made a bit faster by combining writes
 	 * to the catmap instead of setting a single bit each time, but for
@@ -596,7 +604,9 @@ int netlbl_secattr_catmap_setrng(struct netlbl_lsm_secattr_catmap *catmap,
 			iter = iter->next;
 			iter_max_spot = iter->startbit + NETLBL_CATMAP_SIZE;
 		}
-		ret_val = netlbl_secattr_catmap_setbit(iter, spot, flags);
+		ret_val = netlbl_secattr_catmap_setbit(&iter, spot, flags);
+		if (iter->startbit < orig_spot)
+			*catmap = iter;
 	}
 
 	return ret_val;