[PATCH] ext4: fix NULL pointer dereference from orig_data in fill_super and remount.

[PATCH] ext4: fix NULL pointer dereference from orig_data in fill_super and remount.

[Namjae Jeon]

Fix NULL pointer dereference from orig_data in fill_super and remount.

Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
---
 fs/ext4/super.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9953d80..3770d3f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3102,7 +3102,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 				__releases(kernel_lock)
 				__acquires(kernel_lock)
 {
-	char *orig_data = kstrdup(data, GFP_KERNEL);
 	struct buffer_head *bh;
 	struct ext4_super_block *es = NULL;
 	struct ext4_sb_info *sbi;
@@ -3124,6 +3123,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	int err;
 	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 	ext4_group_t first_not_zeroed;
+
+	char *orig_data = kstrdup(data, GFP_KERNEL);
+	if (!orig_data)
+		return ret;
 
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
 	if (!sbi)
@@ -4398,6 +4401,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	int i;
 #endif
 	char *orig_data = kstrdup(data, GFP_KERNEL);
+	if (!orig_data) {
+		err = -ENOMEM;
+		goto failed_alloc_orig;
+	}
 
 	/* Store the original options */
 	lock_super(sb);
@@ -4562,6 +4569,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	return 0;
 
 restore_opts:
+	kfree(orig_data);
+failed_alloc_orig:
 	sb->s_flags = old_sb_flags;
 	sbi->s_mount_opt = old_opts.s_mount_opt;
 	sbi->s_mount_opt2 = old_opts.s_mount_opt2;
@@ -4580,7 +4589,6 @@ restore_opts:
 	}
 #endif
 	unlock_super(sb);
-	kfree(orig_data);
 	return err;
 }
 
-- 
1.7.4.4

Re: [PATCH] ext4: fix NULL pointer dereference from orig_data in fill_super and remount.

[Srivatsa S. Bhat]

On 11/06/2011 08:49 PM, Namjae Jeon wrote:
> Fix NULL pointer dereference from orig_data in fill_super and remount.
> 
> Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
> ---
>  fs/ext4/super.c |   12 ++++++++++--
>  1 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 9953d80..3770d3f 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3102,7 +3102,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  				__releases(kernel_lock)
>  				__acquires(kernel_lock)
>  {
> -	char *orig_data = kstrdup(data, GFP_KERNEL);
>  	struct buffer_head *bh;
>  	struct ext4_super_block *es = NULL;
>  	struct ext4_sb_info *sbi;
> @@ -3124,6 +3123,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	int err;
>  	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
>  	ext4_group_t first_not_zeroed;
> +
> +	char *orig_data = kstrdup(data, GFP_KERNEL);
> +	if (!orig_data)
> +		return ret;
> 
>  	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>  	if (!sbi)
> @@ -4398,6 +4401,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  	int i;
>  #endif
>  	char *orig_data = kstrdup(data, GFP_KERNEL);
> +	if (!orig_data) {
> +		err = -ENOMEM;
> +		goto failed_alloc_orig;

I didn't quite get why 'failed_alloc_orig' is needed here.
Why can't we just return -ENOMEM? Anyway we haven't yet
clobbered any opts at this point, right?

See my comments below.

> +	}
> 
>  	/* Store the original options */
>  	lock_super(sb);
> @@ -4562,6 +4569,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  	return 0;
> 
>  restore_opts:
> +	kfree(orig_data);
> +failed_alloc_orig:
>  	sb->s_flags = old_sb_flags;
>  	sbi->s_mount_opt = old_opts.s_mount_opt;
>  	sbi->s_mount_opt2 = old_opts.s_mount_opt2;

This would put garbage values in sb->... and sbi->... when we jump
to 'failed_alloc_orig' upon 'orig_data' allocation failure, because
the old_* variables were still uninitialized at that point.

> @@ -4580,7 +4589,6 @@ restore_opts:
>  	}
>  #endif
>  	unlock_super(sb);
> -	kfree(orig_data);
>  	return err;
>  }
> 

Thanks,
Srivatsa S. Bhat

Re: [PATCH] ext4: fix NULL pointer dereference from orig_data in fill_super and remount.

[NamJae Jeon]

2011/11/7 Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>:
> On 11/06/2011 08:49 PM, Namjae Jeon wrote:
>> Fix NULL pointer dereference from orig_data in fill_super and remount.
>>
>> Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
>> ---
>>  fs/ext4/super.c |   12 ++++++++++--
>>  1 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index 9953d80..3770d3f 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -3102,7 +3102,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>                               __releases(kernel_lock)
>>                               __acquires(kernel_lock)
>>  {
>> -     char *orig_data = kstrdup(data, GFP_KERNEL);
>>       struct buffer_head *bh;
>>       struct ext4_super_block *es = NULL;
>>       struct ext4_sb_info *sbi;
>> @@ -3124,6 +3123,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>       int err;
>>       unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
>>       ext4_group_t first_not_zeroed;
>> +
>> +     char *orig_data = kstrdup(data, GFP_KERNEL);
>> +     if (!orig_data)
>> +             return ret;
>>
>>       sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>>       if (!sbi)
>> @@ -4398,6 +4401,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>       int i;
>>  #endif
>>       char *orig_data = kstrdup(data, GFP_KERNEL);
>> +     if (!orig_data) {
>> +             err = -ENOMEM;
>> +             goto failed_alloc_orig;
>
> I didn't quite get why 'failed_alloc_orig' is needed here.
> Why can't we just return -ENOMEM? Anyway we haven't yet
> clobbered any opts at this point, right?
>
> See my comments below.
>
>> +     }
>>
>>       /* Store the original options */
>>       lock_super(sb);
>> @@ -4562,6 +4569,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>       return 0;
>>
>>  restore_opts:
>> +     kfree(orig_data);
>> +failed_alloc_orig:
>>       sb->s_flags = old_sb_flags;
>>       sbi->s_mount_opt = old_opts.s_mount_opt;
>>       sbi->s_mount_opt2 = old_opts.s_mount_opt2;
>
> This would put garbage values in sb->... and sbi->... when we jump
> to 'failed_alloc_orig' upon 'orig_data' allocation failure, because
> the old_* variables were still uninitialized at that point.
>
>> @@ -4580,7 +4589,6 @@ restore_opts:
>>       }
>>  #endif
>>       unlock_super(sb);
>> -     kfree(orig_data);
>>       return err;
>>  }
>>
>
> Thanks,
> Srivatsa S. Bhat
Hi.
Thanks for your review. It's my mistake.
I will post patch v2 after modifing again.
>
>

Re: [PATCH] ext4: fix NULL pointer dereference from orig_data in fill_super and remount.

[Srivatsa S. Bhat]

On 11/07/2011 04:43 AM, NamJae Jeon wrote:
> 2011/11/7 Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>:
>> On 11/06/2011 08:49 PM, Namjae Jeon wrote:
>>> Fix NULL pointer dereference from orig_data in fill_super and remount.
>>>
>>> Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
>>> ---
>>>  fs/ext4/super.c |   12 ++++++++++--
>>>  1 files changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>>> index 9953d80..3770d3f 100644
>>> --- a/fs/ext4/super.c
>>> +++ b/fs/ext4/super.c
>>> @@ -3102,7 +3102,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>>                               __releases(kernel_lock)
>>>                               __acquires(kernel_lock)
>>>  {
>>> -     char *orig_data = kstrdup(data, GFP_KERNEL);
>>>       struct buffer_head *bh;
>>>       struct ext4_super_block *es = NULL;
>>>       struct ext4_sb_info *sbi;
>>> @@ -3124,6 +3123,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>>       int err;
>>>       unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
>>>       ext4_group_t first_not_zeroed;
>>> +
>>> +     char *orig_data = kstrdup(data, GFP_KERNEL);
>>> +     if (!orig_data)
>>> +             return ret;
>>>
>>>       sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>>>       if (!sbi)
>>> @@ -4398,6 +4401,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>>       int i;
>>>  #endif
>>>       char *orig_data = kstrdup(data, GFP_KERNEL);
>>> +     if (!orig_data) {
>>> +             err = -ENOMEM;
>>> +             goto failed_alloc_orig;
>>
>> I didn't quite get why 'failed_alloc_orig' is needed here.
>> Why can't we just return -ENOMEM? Anyway we haven't yet
>> clobbered any opts at this point, right?
>>
>> See my comments below.
>>
>>> +     }
>>>
>>>       /* Store the original options */
>>>       lock_super(sb);
>>> @@ -4562,6 +4569,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>>       return 0;
>>>
>>>  restore_opts:
>>> +     kfree(orig_data);
>>> +failed_alloc_orig:
>>>       sb->s_flags = old_sb_flags;
>>>       sbi->s_mount_opt = old_opts.s_mount_opt;
>>>       sbi->s_mount_opt2 = old_opts.s_mount_opt2;
>>
>> This would put garbage values in sb->... and sbi->... when we jump
>> to 'failed_alloc_orig' upon 'orig_data' allocation failure, because
>> the old_* variables were still uninitialized at that point.
>>
>>> @@ -4580,7 +4589,6 @@ restore_opts:
>>>       }
>>>  #endif
>>>       unlock_super(sb);
>>> -     kfree(orig_data);
>>>       return err;
>>>  }
>>>
>>
>> Thanks,
>> Srivatsa S. Bhat
> Hi.
> Thanks for your review. It's my mistake.
> I will post patch v2 after modifing again.

Sure. And please CC linux-ext4@vger.kernel.org for ext4 related patches.

Thanks,
Srivatsa S. Bhat