diff options
| author | Kal Conley <kal.conley@dectris.com> | 2023-04-11 15:00:25 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-04-13 15:00:11 +0200 |
| commit | 1ba83f505c53d35eda892ac7f108ef1189da6fa8 (patch) | |
| tree | 5ed7d9a1770a21249577fa2608f0e798c576c8b1 /net/xdp | |
| parent | 4099be372faf7b3616634dfe6994b81b1edf1906 (diff) | |
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 <kal.conley@dectris.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20230411130025.19704-1-kal.conley@dectris.com
Diffstat (limited to 'net/xdp')
| -rw-r--r-- | net/xdp/xsk_queue.h | 8 |
1 files changed, 2 insertions, 6 deletions
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; |