[PATCH 2.6.32 26/55] udf: limit the maximum number of indirect extents in a row

[Willy Tarreau]

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Vegard Nossum <vegard.nossum@xxxxxxxxxx>

commit b0918d9f476a8434b055e362b83fa4fd1d462c3f upstream.

udf_next_aext() just follows extent pointers while extents are marked as
indirect. This can loop forever for corrupted filesystem. Limit number
the of indirect extents we are willing to follow in a row.

[JK: Updated changelog, limit, style]

Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxxx>
Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
[wt: udf_error() instead of udf_err() in 2.6.32]
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 fs/udf/inode.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index b8d7a0e..a22f568 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1869,14 +1869,29 @@ int8_t udf_write_aext(struct inode *inode, struct extent_position *epos,
 	return (elen >> 30);
 }
 
+/*
+ * Only 1 indirect extent in a row really makes sense but allow upto 16 in case
+ * someone does some weird stuff.
+ */
+#define UDF_MAX_INDIR_EXTS 16
+
 int8_t udf_next_aext(struct inode *inode, struct extent_position *epos,
 		     struct kernel_lb_addr *eloc, uint32_t *elen, int inc)
 {
 	int8_t etype;
+	unsigned int indirections = 0;
 
 	while ((etype = udf_current_aext(inode, epos, eloc, elen, inc)) ==
 	       (EXT_NEXT_EXTENT_ALLOCDECS >> 30)) {
 		int block;
+
+		if (++indirections > UDF_MAX_INDIR_EXTS) {
+			udf_error(inode->i_sb, __func__,
+				  "too many indirect extents in inode %lu\n",
+				  inode->i_ino);
+			return -1;
+		}
+
 		epos->block = *eloc;
 		epos->offset = sizeof(struct allocExtDesc);
 		brelse(epos->bh);
-- 
1.7.12.2.21.g234cd45.dirty