Merge tag 'afs-fixes-04012021' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull AFS fixes from David Howells:
 "Two fixes.

  The first is the fix for the strnlen() array limit check and the
  second fixes the calculation of the number of dirent records used to
  represent any particular filename length"

* tag 'afs-fixes-04012021' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Fix directory entry size calculation
  afs: Work around strnlen() oops with CONFIG_FORTIFIED_SOURCE=y

1 files changed, 26 insertions, 23 deletions

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 9068d5578a26..7bd659ad959e 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -350,7 +350,7 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode,
 				 unsigned blkoff)
 {
 	union afs_xdr_dirent *dire;
-	unsigned offset, next, curr;
+	unsigned offset, next, curr, nr_slots;
 	size_t nlen;
 	int tmp;
 
@@ -363,13 +363,12 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode,
 	     offset < AFS_DIR_SLOTS_PER_BLOCK;
 	     offset = next
 	     ) {
-		next = offset + 1;
-
 		/* skip entries marked unused in the bitmap */
 		if (!(block->hdr.bitmap[offset / 8] &
 		      (1 << (offset % 8)))) {
 			_debug("ENT[%zu.%u]: unused",
 			       blkoff / sizeof(union afs_xdr_dir_block), offset);
+			next = offset + 1;
 			if (offset >= curr)
 				ctx->pos = blkoff +
 					next * sizeof(union afs_xdr_dirent);
@@ -381,35 +380,39 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode,
 		nlen = strnlen(dire->u.name,
 			       sizeof(*block) -
 			       offset * sizeof(union afs_xdr_dirent));
+		if (nlen > AFSNAMEMAX - 1) {
+			_debug("ENT[%zu]: name too long (len %u/%zu)",
+			       blkoff / sizeof(union afs_xdr_dir_block),
+			       offset, nlen);
+			return afs_bad(dvnode, afs_file_error_dir_name_too_long);
+		}
 
 		_debug("ENT[%zu.%u]: %s %zu \"%s\"",
 		       blkoff / sizeof(union afs_xdr_dir_block), offset,
 		       (offset < curr ? "skip" : "fill"),
 		       nlen, dire->u.name);
 
-		/* work out where the next possible entry is */
-		for (tmp = nlen; tmp > 15; tmp -= sizeof(union afs_xdr_dirent)) {
-			if (next >= AFS_DIR_SLOTS_PER_BLOCK) {
-				_debug("ENT[%zu.%u]:"
-				       " %u travelled beyond end dir block"
-				       " (len %u/%zu)",
-				       blkoff / sizeof(union afs_xdr_dir_block),
-				       offset, next, tmp, nlen);
-				return afs_bad(dvnode, afs_file_error_dir_over_end);
-			}
-			if (!(block->hdr.bitmap[next / 8] &
-			      (1 << (next % 8)))) {
-				_debug("ENT[%zu.%u]:"
-				       " %u unmarked extension (len %u/%zu)",
+		nr_slots = afs_dir_calc_slots(nlen);
+		next = offset + nr_slots;
+		if (next > AFS_DIR_SLOTS_PER_BLOCK) {
+			_debug("ENT[%zu.%u]:"
+			       " %u extends beyond end dir block"
+			       " (len %zu)",
+			       blkoff / sizeof(union afs_xdr_dir_block),
+			       offset, next, nlen);
+			return afs_bad(dvnode, afs_file_error_dir_over_end);
+		}
+
+		/* Check that the name-extension dirents are all allocated */
+		for (tmp = 1; tmp < nr_slots; tmp++) {
+			unsigned int ix = offset + tmp;
+			if (!(block->hdr.bitmap[ix / 8] & (1 << (ix % 8)))) {
+				_debug("ENT[%zu.u]:"
+				       " %u unmarked extension (%u/%u)",
 				       blkoff / sizeof(union afs_xdr_dir_block),
-				       offset, next, tmp, nlen);
+				       offset, tmp, nr_slots);
 				return afs_bad(dvnode, afs_file_error_dir_unmarked_ext);
 			}
-
-			_debug("ENT[%zu.%u]: ext %u/%zu",
-			       blkoff / sizeof(union afs_xdr_dir_block),
-			       next, tmp, nlen);
-			next++;
 		}
 
 		/* skip if starts before the current position */