linux-kernel - Re: [PATCH] pstore/platform: Add check for kstrdup

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Message-Id: <20230615024806.39381-1-jiasheng@iscas.ac.cn>
Date:   Thu, 15 Jun 2023 10:48:06 +0800
From:   Jiasheng Jiang <jiasheng@...as.ac.cn>
To:     keescook@...omium.org
Cc:     tony.luck@...el.com, gpiccoli@...lia.com,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiasheng Jiang <jiasheng@...as.ac.cn>
Subject: Re: [PATCH] pstore/platform: Add check for kstrdup

On Thu, Jun 15, 2023 at 03:01:30PM +0800, Kees Cook wrote:
> On Wed, Jun 14, 2023 at 06:00:20PM +0800, Jiasheng Jiang wrote:
>> Add check for the return value of kstrdup() and return the error
>> if it fails in order to avoid NULL pointer dereference.
>> 
>> Fixes: 563ca40ddf40 ("pstore/platform: Switch pstore_info::name to const")
>> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
>> ---
>>  fs/pstore/platform.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
>> index cbc0b468c1ab..afe07f0d1216 100644
>> --- a/fs/pstore/platform.c
>> +++ b/fs/pstore/platform.c
>> @@ -631,6 +631,10 @@ int pstore_register(struct pstore_info *psi)
>>  	 * through /sys/module/pstore/parameters/backend
>>  	 */
>>  	backend = kstrdup(psi->name, GFP_KERNEL);
>> +	if (!backend) {
>> +		mutex_unlock(&psinfo_lock);
>> +		return -ENOMEM;
>> +	}
> 
> Hmm, I think this isn't the right place since there's been a bunch of
> other allocations and registrations. I think it would be better to
> allocate a copy (but not assign to "backend" yet) earlier, perhaps
> before the taking the psinfo_lock lock? Like:
> 
> 	char *new_backend;
> 	...
> 	new_backend = kstrdup(psi->name, GFP_KERNEL);
> 	if (!new_backend)
> 		return -ENOMEM;
> 
>         mutex_lock(&psinfo_lock);
>         if (psinfo) {
> 		...
>                 mutex_unlock(&psinfo_lock);
> 		kfree(new_backend);
>                 return -EBUSY;
>         }
> 	...
> 	backend = new_backend;

Fine, I will submit a v2 to allocate earlier.

Thanks,
Jiasheng