[PATCH v3] jfs: fix array-index-out-of-bounds in dbFindLeaf

[Manas Ghandat]

Currently while searching for dmtree_t for sufficient free blocks there
is an array out of bounds while getting element in tp->dm_stree. To add
the required check for out of bound we first need to determine the type
of dmtree. Thus added an extra parameter to dbFindLeaf so that the type
of tree can be determined and the required check can be applied.

Reported-by: syzbot+aea1ad91e854d0a83e04@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=aea1ad91e854d0a83e04
Signed-off-by: Manas Ghandat <ghandatmanas@xxxxxxxxx>
---
V2 -> V3: Changed the argument name from type to is_ctl
V1 -> V2: Updated dbFindLeaf function.

 fs/jfs/jfs_dmap.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a14a0f18a4c4..d2a4fced8976 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -87,7 +87,7 @@ static int dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno,
 static int dbExtend(struct inode *ip, s64 blkno, s64 nblocks, s64 addnblocks);
 static int dbFindBits(u32 word, int l2nb);
 static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno);
-static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx);
+static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl);
 static int dbFreeBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
 		      int nblocks);
 static int dbFreeDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
@@ -1709,7 +1709,7 @@ static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno)
 		 * dbFindLeaf() returns the index of the leaf at which
 		 * free space was found.
 		 */
-		rc = dbFindLeaf((dmtree_t *) dcp, l2nb, &leafidx);
+		rc = dbFindLeaf((dmtree_t *) dcp, l2nb, &leafidx, true);
 
 		/* release the buffer.
 		 */
@@ -1956,7 +1956,7 @@ dbAllocDmapLev(struct bmap * bmp,
 	 * free space.  if sufficient free space is found, dbFindLeaf()
 	 * returns the index of the leaf at which free space was found.
 	 */
-	if (dbFindLeaf((dmtree_t *) & dp->tree, l2nb, &leafidx))
+	if (dbFindLeaf((dmtree_t *) &dp->tree, l2nb, &leafidx, false))
 		return -ENOSPC;
 
 	if (leafidx < 0)
@@ -2920,14 +2920,18 @@ static void dbAdjTree(dmtree_t * tp, int leafno, int newval)
  *	leafidx	- return pointer to be set to the index of the leaf
  *		  describing at least l2nb free blocks if sufficient
  *		  free blocks are found.
+ *	is_ctl	- determines if the tree is of type ctl
  *
  * RETURN VALUES:
  *	0	- success
  *	-ENOSPC	- insufficient free blocks.
  */
-static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx)
+static int dbFindLeaf(dmtree_t *tp, int l2nb, int *leafidx, bool is_ctl)
 {
 	int ti, n = 0, k, x = 0;
+	int max_size;
+
+	max_size = is_ctl ? CTLTREESIZE : TREESIZE;
 
 	/* first check the root of the tree to see if there is
 	 * sufficient free space.
@@ -2948,6 +2952,8 @@ static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx)
 			/* sufficient free space found.  move to the next
 			 * level (or quit if this is the last level).
 			 */
+			if (x + n > max_size)
+				return -ENOSPC;
 			if (l2nb <= tp->dmt_stree[x + n])
 				break;
 		}
-- 
2.37.2