netlabel: fix the horribly broken catmap functions

The NetLabel secattr catmap functions, and the SELinux import/export
glue routines, were broken in many horrible ways and the SELinux glue
code fiddled with the NetLabel catmap structures in ways that we
probably shouldn't allow.  At some point this "worked", but that was
likely due to a bit of dumb luck and sub-par testing (both inflicted
by yours truly).  This patch corrects these problems by basically
gutting the code in favor of something less obtuse and restoring the
NetLabel abstractions in the SELinux catmap glue code.

Everything is working now, and if it decides to break itself in the
future this code will be much easier to debug than the code it
replaces.

One noteworthy side effect of the changes is that it is no longer
necessary to allocate a NetLabel catmap before calling one of the
NetLabel APIs to set a bit in the catmap.  NetLabel will automatically
allocate the catmap nodes when needed, resulting in less allocations
when the lowest bit is greater than 255 and less code in the LSMs.

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, 166 insertions, 50 deletions

diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c
index 84e810bef39a..d9e10466b928 100644
--- a/net/netlabel/netlabel_kapi.c
+++ b/net/netlabel/netlabel_kapi.c
@@ -405,6 +405,63 @@ out_entry:
  * Security Attribute Functions
  */
 
+#define _CM_F_NONE	0x00000000
+#define _CM_F_ALLOC	0x00000001
+
+/**
+ * _netlbl_secattr_catmap_getnode - Get a individual node from a catmap
+ * @catmap: pointer to the category bitmap
+ * @offset: the requested offset
+ * @cm_flags: catmap flags, see _CM_F_*
+ * @gfp_flags: memory allocation flags
+ *
+ * Description:
+ * Iterate through the catmap looking for the node associated with @offset; if
+ * the _CM_F_ALLOC flag is set in @cm_flags and there is no associated node,
+ * one will be created and inserted into the catmap.  Returns a pointer to the
+ * node on success, NULL on failure.
+ *
+ */
+static struct netlbl_lsm_secattr_catmap *_netlbl_secattr_catmap_getnode(
+				struct netlbl_lsm_secattr_catmap **catmap,
+				u32 offset,
+				unsigned int cm_flags,
+				gfp_t gfp_flags)
+{
+	struct netlbl_lsm_secattr_catmap *iter = *catmap;
+	struct netlbl_lsm_secattr_catmap *prev = NULL;
+
+	if (iter == NULL || offset < iter->startbit)
+		goto secattr_catmap_getnode_alloc;
+	while (iter && offset >= (iter->startbit + NETLBL_CATMAP_SIZE)) {
+		prev = iter;
+		iter = iter->next;
+	}
+	if (iter == NULL || offset < iter->startbit)
+		goto secattr_catmap_getnode_alloc;
+
+	return iter;
+
+secattr_catmap_getnode_alloc:
+	if (!(cm_flags & _CM_F_ALLOC))
+		return NULL;
+
+	iter = netlbl_secattr_catmap_alloc(gfp_flags);
+	if (iter == NULL)
+		return NULL;
+	iter->startbit = offset & ~(NETLBL_CATMAP_SIZE - 1);
+
+	if (prev == NULL) {
+		iter->next = *catmap;
+		*catmap = iter;
+	} else {
+		iter->next = prev->next;
+		prev->next = iter;
+	}
+
+	return iter;
+}
+
 /**
  * netlbl_secattr_catmap_walk - Walk a LSM secattr catmap looking for a bit
  * @catmap: the category bitmap
@@ -521,6 +578,54 @@ int netlbl_secattr_catmap_walk_rng(struct netlbl_lsm_secattr_catmap *catmap,
 }
 
 /**
+ * netlbl_secattr_catmap_getlong - Export an unsigned long bitmap
+ * @catmap: pointer to the category bitmap
+ * @offset: pointer to the requested offset
+ * @bitmap: the exported bitmap
+ *
+ * Description:
+ * Export a bitmap with an offset greater than or equal to @offset and return
+ * it in @bitmap.  The @offset must be aligned to an unsigned long and will be
+ * updated on return if different from what was requested; if the catmap is
+ * empty at the requested offset and beyond, the @offset is set to (u32)-1.
+ * Returns zero on sucess, negative values on failure.
+ *
+ */
+int netlbl_secattr_catmap_getlong(struct netlbl_lsm_secattr_catmap *catmap,
+				  u32 *offset,
+				  unsigned long *bitmap)
+{
+	struct netlbl_lsm_secattr_catmap *iter;
+	u32 off = *offset;
+	u32 idx;
+
+	/* only allow aligned offsets */
+	if ((off & (BITS_PER_LONG - 1)) != 0)
+		return -EINVAL;
+
+	if (off < catmap->startbit) {
+		off = catmap->startbit;
+		*offset = off;
+	}
+	iter = _netlbl_secattr_catmap_getnode(&catmap, off, _CM_F_NONE, 0);
+	if (iter == NULL) {
+		*offset = (u32)-1;
+		return 0;
+	}
+
+	if (off < iter->startbit) {
+		off = iter->startbit;
+		*offset = off;
+	} else
+		off -= iter->startbit;
+
+	idx = off / NETLBL_CATMAP_MAPSIZE;
+	*bitmap = iter->bitmap[idx] >> (off % NETLBL_CATMAP_SIZE);
+
+	return 0;
+}
+
+/**
  * netlbl_secattr_catmap_setbit - Set a bit in a LSM secattr catmap
  * @catmap: pointer to the category bitmap
  * @bit: the bit to set
@@ -535,32 +640,16 @@ int netlbl_secattr_catmap_setbit(struct netlbl_lsm_secattr_catmap **catmap,
 				 u32 bit,
 				 gfp_t flags)
 {
-	struct netlbl_lsm_secattr_catmap *iter = *catmap;
-	u32 node_bit;
-	u32 node_idx;
+	struct netlbl_lsm_secattr_catmap *iter;
+	u32 idx;
 
-	while (iter->next != NULL &&
-	       bit >= (iter->startbit + NETLBL_CATMAP_SIZE))
-		iter = iter->next;
-	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;
-		iter = iter->next;
-		iter->startbit = bit & ~(NETLBL_CATMAP_SIZE - 1);
-	}
+	iter = _netlbl_secattr_catmap_getnode(catmap, bit, _CM_F_ALLOC, flags);
+	if (iter == NULL)
+		return -ENOMEM;
 
-	/* gcc always rounds to zero when doing integer division */
-	node_idx = (bit - iter->startbit) / NETLBL_CATMAP_MAPSIZE;
-	node_bit = bit - iter->startbit - (NETLBL_CATMAP_MAPSIZE * node_idx);
-	iter->bitmap[node_idx] |= NETLBL_CATMAP_BIT << node_bit;
+	bit -= iter->startbit;
+	idx = bit / NETLBL_CATMAP_MAPSIZE;
+	iter->bitmap[idx] |= NETLBL_CATMAP_BIT << (bit % NETLBL_CATMAP_MAPSIZE);
 
 	return 0;
 }
@@ -582,34 +671,61 @@ int netlbl_secattr_catmap_setrng(struct netlbl_lsm_secattr_catmap **catmap,
 				 u32 end,
 				 gfp_t flags)
 {
-	int ret_val = 0;
-	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
-	 * right now skipping to the start of the range in the catmap should
-	 * be a nice improvement over calling the individual setbit function
-	 * repeatedly from a loop. */
-
-	while (iter->next != NULL &&
-	       start >= (iter->startbit + NETLBL_CATMAP_SIZE))
-		iter = iter->next;
-	iter_max_spot = iter->startbit + NETLBL_CATMAP_SIZE;
-
-	for (spot = start; spot <= end && ret_val == 0; spot++) {
-		if (spot >= iter_max_spot && iter->next != NULL) {
-			iter = iter->next;
-			iter_max_spot = iter->startbit + NETLBL_CATMAP_SIZE;
-		}
-		ret_val = netlbl_secattr_catmap_setbit(&iter, spot, flags);
-		if (iter->startbit < orig_spot)
-			*catmap = iter;
+	int rc = 0;
+	u32 spot = start;
+
+	while (rc == 0 && spot <= end) {
+		if (((spot & (BITS_PER_LONG - 1)) != 0) &&
+		    ((end - spot) > BITS_PER_LONG)) {
+			rc = netlbl_secattr_catmap_setlong(catmap,
+							   spot,
+							   (unsigned long)-1,
+							   flags);
+			spot += BITS_PER_LONG;
+		} else
+			rc = netlbl_secattr_catmap_setbit(catmap,
+							  spot++,
+							  flags);
 	}
 
-	return ret_val;
+	return rc;
+}
+
+/**
+ * netlbl_secattr_catmap_setlong - Import an unsigned long bitmap
+ * @catmap: pointer to the category bitmap
+ * @offset: offset to the start of the imported bitmap
+ * @bitmap: the bitmap to import
+ * @flags: memory allocation flags
+ *
+ * Description:
+ * Import the bitmap specified in @bitmap into @catmap, using the offset
+ * in @offset.  The offset must be aligned to an unsigned long.  Returns zero
+ * on success, negative values on failure.
+ *
+ */
+int netlbl_secattr_catmap_setlong(struct netlbl_lsm_secattr_catmap **catmap,
+				  u32 offset,
+				  unsigned long bitmap,
+				  gfp_t flags)
+{
+	struct netlbl_lsm_secattr_catmap *iter;
+	u32 idx;
+
+	/* only allow aligned offsets */
+	if ((offset & (BITS_PER_LONG - 1)) != 0)
+		return -EINVAL;
+
+	iter = _netlbl_secattr_catmap_getnode(catmap,
+					      offset, _CM_F_ALLOC, flags);
+	if (iter == NULL)
+		return -ENOMEM;
+
+	offset -= iter->startbit;
+	idx = offset / NETLBL_CATMAP_MAPSIZE;
+	iter->bitmap[idx] |= bitmap << (offset % NETLBL_CATMAP_MAPSIZE);
+
+	return 0;
 }
 
 /*