We did not implement any bound on number of indirect ICBs we follow when
loading inode. Thus corrupted medium could cause kernel to go into an
infinite loop, possibly causing a stack overflow.
Fix the possible stack overflow by removing recursion from
__udf_read_inode() and limit number of indirect ICBs we follow to avoid
infinite loops.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/udf/inode.c | 35 +++++++++++++++++++++--------------
1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 68cc7b144c26..a6a40536ebf1 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1270,6 +1270,13 @@ update_time:
return 0;
}
+/*
+ * Maximum length of linked list formed by ICB hierarchy. The chosen number is
+ * arbitrary - just that we hopefully don't limit any real use of rewritten
+ * inode on write-once media but avoid looping for too long on corrupted media.
+ */
+#define UDF_MAX_ICB_NESTING 1024
+
static void __udf_read_inode(struct inode *inode)
{
struct buffer_head *bh = NULL;
@@ -1279,7 +1286,9 @@ static void __udf_read_inode(struct inode *inode)
struct udf_inode_info *iinfo = UDF_I(inode);
struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
unsigned int link_count;
+ unsigned int indirections = 0;
+reread:
/*
* Set defaults, but the inode is still incomplete!
* Note: get_new_inode() sets the following on a new inode:
@@ -1317,28 +1326,26 @@ static void __udf_read_inode(struct inode *inode)
ibh = udf_read_ptagged(inode->i_sb, &iinfo->i_location, 1,
&ident);
if (ident == TAG_IDENT_IE && ibh) {
- struct buffer_head *nbh = NULL;
struct kernel_lb_addr loc;
struct indirectEntry *ie;
ie = (struct indirectEntry *)ibh->b_data;
loc = lelb_to_cpu(ie->indirectICB.extLocation);
- if (ie->indirectICB.extLength &&
- (nbh = udf_read_ptagged(inode->i_sb, &loc, 0,
- &ident))) {
- if (ident == TAG_IDENT_FE ||
- ident == TAG_IDENT_EFE) {
- memcpy(&iinfo->i_location,
- &loc,
- sizeof(struct kernel_lb_addr));
- brelse(bh);
- brelse(ibh);
- brelse(nbh);
- __udf_read_inode(inode);
+ if (ie->indirectICB.extLength) {
+ brelse(bh);
+ brelse(ibh);
+ memcpy(&iinfo->i_location, &loc,
+ sizeof(struct kernel_lb_addr));
+ if (++indirections > UDF_MAX_ICB_NESTING) {
+ udf_err(inode->i_sb,
+ "too many ICBs in ICB hierarchy"
+ " (max %d supported)\n",
+ UDF_MAX_ICB_NESTING);
+ make_bad_inode(inode);
return;
}
- brelse(nbh);
+ goto reread;
}
}
brelse(ibh);
--
1.8.1.4
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