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@xxxxxxxxxx>
---
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
