[PATCH] fs/proc/task_mmu: prevent integer overflow in pagemap_scan_get_args()

[Dan Carpenter <dan.carpenter@linaro.org>]

The "arg->vec_len" variable is a u64 that comes from the user at the
start of the function.  The "arg->vec_len * sizeof(struct page_region))"
multiplication can lead to integer wrapping.  Use size_mul() to avoid
that.

Also the size_add/mul() functions work on unsigned long so for 32bit
systems we need to ensure that "arg->vec_len" fits in an unsigned long.

Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 fs/proc/task_mmu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index f57ea9b308bb..38a5a3e9cba2 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2665,8 +2665,10 @@ static int pagemap_scan_get_args(struct pm_scan_arg *arg,
 		return -EFAULT;
 	if (!arg->vec && arg->vec_len)
 		return -EINVAL;
+	if (UINT_MAX == SIZE_MAX && arg->vec_len > SIZE_MAX)
+		return -EINVAL;
 	if (arg->vec && !access_ok((void __user *)(long)arg->vec,
-			      arg->vec_len * sizeof(struct page_region)))
+				   size_mul(arg->vec_len, sizeof(struct page_region))))
 		return -EFAULT;
 
 	/* Fixup default values */
-- 
2.45.2