ext4: fix potential integer overflow in alloc_flex_gd()
In alloc_flex_gd(), when flexbg_size is large, kmalloc size would
overflow and flex_gd->groups would point to a buffer smaller than
expected, causing OOB accesses when it is used.
Note that in ext4_resize_fs(), flexbg_size is calculated using
sbi->s_log_groups_per_flex, which is read from the disk and only bounded
to [1, 31]. The patch returns NULL for too large flexbg_size.
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Haogang Chen <haogangchen@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a58ce7c..05c7979 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -161,6 +161,8 @@
if (flex_gd == NULL)
goto out3;
+ if (flexbg_size >= UINT_MAX / sizeof(struct ext4_new_flex_group_data))
+ goto out2;
flex_gd->count = flexbg_size;
flex_gd->groups = kmalloc(sizeof(struct ext4_new_group_data) *