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| author | Dan Carpenter <dan.carpenter@oracle.com> | 2020-02-28 10:22:56 +0100 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2020-02-29 23:48:08 +0100 |
| commit | 37b0b6b8b99c0e1c1f11abbe7cf49b6d03795b3f (patch) | |
| tree | e5b072f6e69c2b726c70c865015763d395680d6a | |
| parent | jbd2: fix data races at struct journal_head (diff) | |
| download | linux-37b0b6b8b99c0e1c1f11abbe7cf49b6d03795b3f.tar.xz linux-37b0b6b8b99c0e1c1f11abbe7cf49b6d03795b3f.zip | |
ext4: potential crash on allocation error in ext4_alloc_flex_bg_array()
If sbi->s_flex_groups_allocated is zero and the first allocation fails
then this code will crash. The problem is that "i--" will set "i" to
-1 but when we compare "i >= sbi->s_flex_groups_allocated" then the -1
is type promoted to unsigned and becomes UINT_MAX. Since UINT_MAX
is more than zero, the condition is true so we call kvfree(new_groups[-1]).
The loop will carry on freeing invalid memory until it crashes.
Fixes: 7c990728b99e ("ext4: fix potential race between s_flex_groups online resizing and access")
Reviewed-by: Suraj Jitindar Singh <surajjs@amazon.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20200228092142.7irbc44yaz3by7nb@kili.mountain
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/super.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index ff1b764b0c0e..0c7c4adb664e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2391,7 +2391,7 @@ int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup) { struct ext4_sb_info *sbi = EXT4_SB(sb); struct flex_groups **old_groups, **new_groups; - int size, i; + int size, i, j; if (!sbi->s_log_groups_per_flex) return 0; @@ -2412,8 +2412,8 @@ int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup) sizeof(struct flex_groups)), GFP_KERNEL); if (!new_groups[i]) { - for (i--; i >= sbi->s_flex_groups_allocated; i--) - kvfree(new_groups[i]); + for (j = sbi->s_flex_groups_allocated; j < i; j++) + kvfree(new_groups[j]); kvfree(new_groups); ext4_msg(sb, KERN_ERR, "not enough memory for %d flex groups", size); |