| From 9f7c2728cac43ccaacbf8def1af84ea912aefa66 Mon Sep 17 00:00:00 2001 |
| From: Dan Carpenter <dan.carpenter@oracle.com> |
| Date: Fri, 28 Feb 2020 12:22:56 +0300 |
| Subject: [PATCH] ext4: potential crash on allocation error in |
| ext4_alloc_flex_bg_array() |
| |
| commit 37b0b6b8b99c0e1c1f11abbe7cf49b6d03795b3f upstream. |
| |
| 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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/fs/ext4/super.c b/fs/ext4/super.c |
| index 6a82443f1e81..c88c6182e502 100644 |
| --- a/fs/ext4/super.c |
| +++ b/fs/ext4/super.c |
| @@ -2332,7 +2332,7 @@ 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; |
| @@ -2353,8 +2353,8 @@ 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); |
| -- |
| 2.7.4 |
| |
