From 1ba83f505c53d35eda892ac7f108ef1189da6fa8 Mon Sep 17 00:00:00 2001 From: Kal Conley Date: Tue, 11 Apr 2023 15:00:25 +0200 Subject: xsk: Elide base_addr comparison in xp_unaligned_validate_desc Remove redundant (base_addr >= pool->addrs_cnt) comparison from the conditional. In particular, addr is computed as: addr = base_addr + offset ... where base_addr and offset are stored as 48-bit and 16-bit unsigned integers, respectively. The above sum cannot overflow u64 since base_addr has a maximum value of 0x0000ffffffffffff and offset has a maximum value of 0xffff (implying a maximum sum of 0x000100000000fffe). Since overflow is impossible, it follows that addr >= base_addr. Now if (base_addr >= pool->addrs_cnt), then clearly: addr >= base_addr >= pool->addrs_cnt Thus, (base_addr >= pool->addrs_cnt) implies (addr >= pool->addrs_cnt). Subsequently, the former comparison is unnecessary in the conditional since for any boolean expressions A and B, (A || B) && (A -> B) is equivalent to B. Signed-off-by: Kal Conley Signed-off-by: Daniel Borkmann Acked-by: Magnus Karlsson Link: https://lore.kernel.org/bpf/20230411130025.19704-1-kal.conley@dectris.com --- net/xdp/xsk_queue.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'net/xdp') diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h index 76b574bffd4a..6d40a77fccbe 100644 --- a/net/xdp/xsk_queue.h +++ b/net/xdp/xsk_queue.h @@ -149,16 +149,12 @@ static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool, static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc) { - u64 addr, base_addr; - - base_addr = xp_unaligned_extract_addr(desc->addr); - addr = xp_unaligned_add_offset_to_addr(desc->addr); + u64 addr = xp_unaligned_add_offset_to_addr(desc->addr); if (desc->len > pool->chunk_size) return false; - if (base_addr >= pool->addrs_cnt || addr >= pool->addrs_cnt || - addr + desc->len > pool->addrs_cnt || + if (addr >= pool->addrs_cnt || addr + desc->len > pool->addrs_cnt || xp_desc_crosses_non_contig_pg(pool, addr, desc->len)) return false; -- cgit v1.2.3-58-ga151