On Tue, Oct 27, 2020 at 6:08 PM Joe Perches joe@perches.com wrote:
On Tue, 2020-10-27 at 17:58 +0100, Bartosz Golaszewski wrote:
On Tue, Oct 27, 2020 at 5:50 PM Joe Perches joe@perches.com wrote:
On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
From: Bartosz Golaszewski bgolaszewski@baylibre.com
Use the helper that checks for overflows internally instead of manually calculating the size of the new array.
Signed-off-by: Bartosz Golaszewski bgolaszewski@baylibre.com
No problem with the patch, it does introduce some symmetry in the code.
Perhaps more symmetry by using kmemdup
drivers/vhost/vringh.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-)
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 8bd8b403f087..99222a3651cd 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh, static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp) { struct kvec *new;
unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;size_t size; if (new_num < 8) new_num = 8;
flag = (iov->max_num & VRINGH_IOV_ALLOCATED);if (flag)new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);else {new = kmalloc_array(new_num, sizeof(struct iovec), gfp);if (new) {memcpy(new, iov->iov,iov->max_num * sizeof(struct iovec));flag = VRINGH_IOV_ALLOCATED;}}
if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec), &size)))return -ENOMEM;The whole point of using helpers such as kmalloc_array() is not doing these checks manually.
Tradeoffs for in readability for overflow and not mistyping or doing the multiplication of iov->max_num * sizeof(struct iovec) twice.
It's out of scope for this series - I want to add users for krealloc_array(), not refactor code I don't really know. If the maintainer of this bit objects, it can be dropped.
Just fyi:
the realloc doesn't do a multiplication overflow test as written so the suggestion is slightly more resistant to defect.
I'm not sure what your point is. I used krealloc_array() exactly for this reason - to add the overflow test.
BTW I suppose kmalloc_array() here can be replaced with krealloc_array() if the original pointer is NULL the first time it's called.
Bartosz