Aneesh Kumar K.V wrote:
> On Fri, Apr 18, 2008 at 10:44:14AM +0530, Aneesh Kumar K.V wrote:
>> On Thu, Apr 17, 2008 at 08:29:18PM +0200, Roel Kluin wrote:
>>> Aneesh Kumar K.V wrote:
>>>
>>>> The function needs more changes. For ex:
>>>>
>>>> 2279 if (meta_group_info[j] == NULL) {
>>>> 2280 printk(KERN_ERR "EXT4-fs: can't allocate buddy mem\n");
>>>> 2281 i--;
>>>> 2282 goto err_freebuddy;
>>>> 2283 }
>>>>
>>>> That decrement i--; could result in bad value if i == 0;.
>> Won't this also have a memory corruption ? Let's say we fail in the first
>> loop itslef. That's with i = 0, and since we are using kmalloc.
>> we may find sbi->s_group_info[0] having some random values. So the
>> kfree can crash. Why not a simple change like below ?
>>
>
> Updated one.
>
Won't this work as well?
---
In ext4_mb_init_backend() 'i' is of type ext4_group_t. Since unsigned, i >= 0 is
always true, so fix hot spins after err_freebuddy: and -meta: and prevent
decrements when zero.
Signed-off-by: Roel Kluin <12o3l@xxxxxxxxxx>
---
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index ef97f19..054cd33 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2572,13 +2572,13 @@ static int ext4_mb_init_backend(struct super_block *sb)
meta_group_info[j] = kzalloc(len, GFP_KERNEL);
if (meta_group_info[j] == NULL) {
printk(KERN_ERR "EXT4-fs: can't allocate buddy mem\n");
- i--;
goto err_freebuddy;
}
desc = ext4_get_group_desc(sb, i, NULL);
if (desc == NULL) {
printk(KERN_ERR
"EXT4-fs: can't read descriptor %lu\n", i);
+ i++;
goto err_freebuddy;
}
memset(meta_group_info[j], 0, len);
@@ -2618,13 +2618,11 @@ static int ext4_mb_init_backend(struct super_block *sb)
return 0;
err_freebuddy:
- while (i >= 0) {
+ while (i-- > 0)
kfree(ext4_get_group_info(sb, i));
- i--;
- }
i = num_meta_group_infos;
err_freemeta:
- while (--i >= 0)
+ while (i-- > 0)
kfree(sbi->s_group_info[i]);
iput(sbi->s_buddy_cache);
err_freesgi:
--
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