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`:
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