[PATCH] pstore/platform: Add check for kstrdup

[PATCH] pstore/platform: Add check for kstrdup

[Jiasheng Jiang]

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@iscas.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;
+	}
 
 	pr_info("Registered %s as persistent store backend\n", psi->name);
 
-- 
2.25.1

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

[Kees Cook]

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@iscas.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;


-Kees

-- 
Kees Cook

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

[Jiasheng Jiang]

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@iscas.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