Patchwork check NULL pointer

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Submitter Shaohua Li
Date June 9, 2011, 3:31 a.m.
Message ID <1307590292.15392.71.camel@sli10-conroe>
Download mbox | patch
Permalink /patch/99611/
State Superseded
Headers show

Comments

Shaohua Li - June 9, 2011, 3:31 a.m.
orig_data could be NULL.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>



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Lukas Czerner - June 9, 2011, 9:24 a.m.
On Thu, 9 Jun 2011, Shaohua Li wrote:

> orig_data could be NULL.

Now, that is the commit description :). Could you please be more
descriptive in the "descritpion" ? Also the subject is not right either,
please see Documentation/SubmittingPatches

Thanks!
-Lukas

> 
> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index cc5c157..45fc255 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3057,6 +3057,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
>  	ext4_group_t first_not_zeroed;
>  
> +	if (!orig_data)
> +		return ret;

Again no data, no reason for backing off.

>  	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>  	if (!sbi)
>  		goto out_free_orig;
> @@ -4285,6 +4287,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  #endif
>  	char *orig_data = kstrdup(data, GFP_KERNEL);
>  
> +	if (!orig_data)
> +		return -ENOMEM;


This does not seem right, it there is no data we will end with ENOMEM
for no reason.

>  	/* Store the original options */
>  	lock_super(sb);
>  	old_sb_flags = sb->s_flags;
> 
> 
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Eric Sandeen - June 9, 2011, 2:51 p.m.
On 6/9/11 4:24 AM, Lukas Czerner wrote:
> On Thu, 9 Jun 2011, Shaohua Li wrote:
> 
>> orig_data could be NULL.
> 
> Now, that is the commit description :). Could you please be more
> descriptive in the "descritpion" ? Also the subject is not right either,
> please see Documentation/SubmittingPatches

Yes; if possible please use the commit message to describe how/why orig_data
can be NULL; a testcase if one exists; the resulting flaw (null pointer deref?)
etc.

something like:

Subject: [PATCH] ext4: check for NULL orig_data pointer in mount paths

The orig_data pointer in ext4_fill_super()  and ext4_remount()
can be null if < ??? >, which can lead to < ??? > in the mount
and remount paths.  This can be demonstrated by < ??? >.  
To avoid this, we can simply test for the null pointer
and return an error in ext4_fill_super() and ext4_remount().


> Thanks!
> -Lukas
> 
>>
>> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index cc5c157..45fc255 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -3057,6 +3057,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>  	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
>>  	ext4_group_t first_not_zeroed;
>>  
>> +	if (!orig_data)
>> +		return ret;
> 
> Again no data, no reason for backing off.

orig_data could be NULL if *data is NULL, or if kstrdup got ENOMEM.

Anyway, please describe how the bug can arise, and then we can better evaluate the change.

Thanks!

-Eric

>>  	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>>  	if (!sbi)
>>  		goto out_free_orig;
>> @@ -4285,6 +4287,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>  #endif
>>  	char *orig_data = kstrdup(data, GFP_KERNEL);
>>  
>> +	if (!orig_data)
>> +		return -ENOMEM;
> 
> 
> This does not seem right, it there is no data we will end with ENOMEM
> for no reason.
> 
>>  	/* Store the original options */
>>  	lock_super(sb);
>>  	old_sb_flags = sb->s_flags;
>>
>>
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>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>> the body of a message to majordomo@vger.kernel.org
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>>
> 

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Patch

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cc5c157..45fc255 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3057,6 +3057,8 @@  static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 	ext4_group_t first_not_zeroed;
 
+	if (!orig_data)
+		return ret;
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
 	if (!sbi)
 		goto out_free_orig;
@@ -4285,6 +4287,8 @@  static int ext4_remount(struct super_block *sb, int *flags, char *data)
 #endif
 	char *orig_data = kstrdup(data, GFP_KERNEL);
 
+	if (!orig_data)
+		return -ENOMEM;
 	/* Store the original options */
 	lock_super(sb);
 	old_sb_flags = sb->s_flags;