lkml.org 
[lkml]   [2023]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] udmabuf: Fix a potential (and unlikely) access to unallocated memory
From
Le 18/09/2023 à 05:10, Gustavo A. R. Silva a écrit :
>
>
> On 9/18/23 12:46, Christophe JAILLET wrote:
>> If 'list_limit' is set to a very high value, 'lsize' computation could
>> overflow if 'head.count' is big enough.
>>
>> In such a case, udmabuf_create() will access to memory beyond 'list'.
>>
>> Use size_mul() to saturate the value, and have memdup_user() fail.
>>
>> Fixes: fbb0de795078 ("Add udmabuf misc device")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>>   drivers/dma-buf/udmabuf.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
>> index c40645999648..fb4c4b5b3332 100644
>> --- a/drivers/dma-buf/udmabuf.c
>> +++ b/drivers/dma-buf/udmabuf.c
>> @@ -314,13 +314,13 @@ static long udmabuf_ioctl_create_list(struct
>> file *filp, unsigned long arg)
>>       struct udmabuf_create_list head;
>>       struct udmabuf_create_item *list;
>>       int ret = -EINVAL;
>> -    u32 lsize;
>> +    size_t lsize;
>>       if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
>>           return -EFAULT;
>>       if (head.count > list_limit)
>>           return -EINVAL;
>> -    lsize = sizeof(struct udmabuf_create_item) * head.count;
>> +    lsize = size_mul(sizeof(struct udmabuf_create_item), head.count);
>>       list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
>>       if (IS_ERR(list))
>>           return PTR_ERR(list);
>
> How about this, and we get rid of `lsize`:

Keeping or removing lsize is mostly a matter of taste, I think.

Using sizeof(*list) is better.

Let see if there are some other comments, and I'll send a v2.

Thanks for the feed-back.

CJ

>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index c40645999648..5cf9d849aaa8 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -314,14 +314,13 @@ static long udmabuf_ioctl_create_list(struct file
> *filp, unsigned long arg)
>         struct udmabuf_create_list head;
>         struct udmabuf_create_item *list;
>         int ret = -EINVAL;
> -       u32 lsize;
>
>         if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
>                 return -EFAULT;
>         if (head.count > list_limit)
>                 return -EINVAL;
> -       lsize = sizeof(struct udmabuf_create_item) * head.count;
> -       list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
> +       list = memdup_user((void __user *)(arg + sizeof(head)),
> +                          size_mul(sizeof(*list), head.count));
>         if (IS_ERR(list))
>                 return PTR_ERR(list);
>
>
> --
> Gustavo
>

\
 
 \ /
  Last update: 2023-09-18 21:24    [W:0.161 / U:2.532 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site