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The count is compared against list_limit, but list_limit is a signed module parameter while the count is u32. If the limit is raised too far or made negative, that comparison no longer bounds the count to a range where sizeof(*list) * count fits in the u32 temporary used for the copy length. A wrapped copy length lets memdup_user() copy fewer entries than udmabuf_create() subsequently walks, leading to out-of-bounds reads from the copied list. Take a positive snapshot of the module limit and use memdup_array_user() so the multiplication is checked before copying. Signed-off-by: Yousef Alhouseen --- drivers/dma-buf/udmabuf.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index bced421c0..b4078ec84 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -469,14 +469,15 @@ 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; + int limit; if (copy_from_user(&head, (void __user *)arg, sizeof(head))) return -EFAULT; - if (head.count > list_limit) + limit = READ_ONCE(list_limit); + if (!head.count || limit <= 0 || head.count > limit) return -EINVAL; - lsize = sizeof(struct udmabuf_create_item) * head.count; - list = memdup_user((void __user *)(arg + sizeof(head)), lsize); + list = memdup_array_user((void __user *)(arg + sizeof(head)), + head.count, sizeof(*list)); if (IS_ERR(list)) return PTR_ERR(list); -- 2.54.0