[PATCH 4.9 079/151] fs/hfs/extent.c: fix array out of bounds read of array extent

[Greg Kroah-Hartman]

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

[ Upstream commit 6c9a3f843a29d6894dfc40df338b91dbd78f0ae3 ]

Currently extent and index i are both being incremented causing an array
out of bounds read on extent[i].  Fix this by removing the extraneous
increment of extent.

Ernesto said:

: This is only triggered when deleting a file with a resource fork.  I
: may be wrong because the documentation isn't clear, but I don't think
: you can create those under linux.  So I guess nobody was testing them.
:
: > A disk space leak, perhaps?
:
: That's what it looks like in general.  hfs_free_extents() won't do
: anything if the block count doesn't add up, and the error will be
: ignored.  Now, if the block count randomly does add up, we could see
: some corruption.

Detected by CoverityScan, CID#711541 ("Out of bounds read")

Link: http://lkml.kernel.org/r/20180831140538.31566-1-colin.king@xxxxxxxxxxxxx
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Reviewed-by: Ernesto A. Fernndez <ernesto.mnd.fernandez@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Hin-Tak Leung <htl10@xxxxxxxxxxxxxxxxxxxxx>
Cc: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/hfs/extent.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfs/extent.c b/fs/hfs/extent.c
index 16819d2a978b4..cbe4fca96378a 100644
--- a/fs/hfs/extent.c
+++ b/fs/hfs/extent.c
@@ -304,7 +304,7 @@ int hfs_free_fork(struct super_block *sb, struct hfs_cat_file *file, int type)
 		return 0;
 
 	blocks = 0;
-	for (i = 0; i < 3; extent++, i++)
+	for (i = 0; i < 3; i++)
 		blocks += be16_to_cpu(extent[i].count);
 
 	res = hfs_free_extents(sb, extent, blocks, blocks);
-- 
2.20.1