patch "genwqe: Prevent an integer overflow in the ioctl" added to char-misc-linus

This is a note to let you know that I've just added the patch titled

genwqe: Prevent an integer overflow in the ioctl

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 110080cea0d0e4dfdb0b536e7f8a5633ead6a781 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <[email protected]>
Date: Tue, 7 May 2019 11:36:34 +0300
Subject: genwqe: Prevent an integer overflow in the ioctl

There are a couple potential integer overflows here.

	round_up(m->size + (m->addr & ~PAGE_MASK), PAGE_SIZE);

The first thing is that the "m->size + (...)" addition could overflow, and the second is that round_up() overflows to zero if the result is within PAGE_SIZE of the type max.

In this code, the "m->size" variable is an u64 but we're saving the result in "map_size" which is an unsigned long and genwqe_user_vmap() takes an unsigned long as well. So I have used ULONG_MAX as the upper bound. From a practical perspective unsigned long is fine/better than trying to change all the types to u64.

---
 drivers/misc/genwqe/card_dev.c   | 2 ++
 drivers/misc/genwqe/card_utils.c | 4 ++++
 2 files changed, 6 insertions(+)

index 8c1b63a4337b..d2098b4d2945 100644
@@ -780,6 +780,8 @@ static int genwqe_pin_mem(struct genwqe_file *cfile, struct genwqe_mem *m)
 
 	if ((m->addr == 0x0) || (m->size == 0))
 		return -EINVAL;
+	if (m->size > ULONG_MAX - PAGE_SIZE - (m->addr & ~PAGE_MASK))
+		return -EINVAL;
 
 	map_addr = (m->addr & PAGE_MASK);
 	map_size = round_up(m->size + (m->addr & ~PAGE_MASK), PAGE_SIZE);

index 89cff9d1012b..7571700abc6e 100644
@@ -586,6 +586,10 @@ int genwqe_user_vmap(struct genwqe_dev *cd, struct dma_mapping *m, void *uaddr,
 	/* determine space needed for page_list. */
 	data = (unsigned long)uaddr;
 	offs = offset_in_page(data);
+	if (size > ULONG_MAX - PAGE_SIZE - offs) {
+		m->size = 0;	/* mark unused and not added */
+		return -EINVAL;
+	}
 	m->nr_pages = DIV_ROUND_UP(offs + size, PAGE_SIZE);
 
 	m->page_list = kcalloc(m->nr_pages,

2.21.0