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Subject[PATCH] FS: ext4: fix integer overflow in alloc_flex_gd()
Date
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.

Signed-off-by: Haogang Chen <haogangchen@gmail.com>
---
fs/ext4/resize.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index f9d948f..8601f4b 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -161,6 +161,8 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned long flexbg_size)
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) *
--
1.7.5.4


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