Re: [PATCH bpf] xsk: add overflow check for u64 division, stored into u32

On 5/25/20 10:03 AM, Björn Töpel wrote:

From: Björn Töpel <redacted>

The npgs member of struct xdp_umem is an u32 entity, and stores the
number of pages the UMEM consumes. The calculation of npgs

   npgs = size / PAGE_SIZE

can overflow.

To avoid overflow scenarios, the division is now first stored in a
u64, and the result is verified to fit into 32b.

An alternative would be storing the npgs as a u64, however, this
wastes memory and is an unrealisticly large packet area.

Link: https://lore.kernel.org/bpf/CACtPs=GGvV-_Yj6rbpzTVnopgi5nhMoCcTkSkYrJHGQHJWFZMQ@mail.gmail.com/ (local)
Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Reported-by: "Minh Bùi Quang" <redacted>
Signed-off-by: Björn Töpel <redacted>

Applied, thanks!