[PATCH 3.10 31/54] udf: limit the maximum number of indirect extents in a row

Greg Kroah-Hartman
2016-02-24T04:01:09Z

From: Vegard Nossum <vegard.nossum@oracle.com>

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@oracle.com>
Cc: Jan Kara <jack@suse.com>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/udf/inode.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -2055,14 +2055,29 @@ void udf_write_aext(struct inode *inode,
epos->offset += adsize;
}

+/*
+ * 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_err(inode->i_sb,
+ "too many indirect extents in inode %lu\n",
+ inode->i_ino);
+ return -1;
+ }
+
epos->block = *eloc;
epos->offset = sizeof(struct allocExtDesc);
brelse(epos->bh);