[PATCH 5.10 160/289] xsk: Fix for xp_aligned_validate_desc() when len == chunk_size

[Greg Kroah-Hartman]

From: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>

[ Upstream commit ac31565c21937eee9117e43c9cd34f557f6f1cb8 ]

When desc->len is equal to chunk_size, it is legal. But when the
xp_aligned_validate_desc() got chunk_end from desc->addr + desc->len
pointing to the next chunk during the check, it caused the check to
fail.

This problem was first introduced in bbff2f321a86 ("xsk: new descriptor
addressing scheme"). Later in 2b43470add8c ("xsk: Introduce AF_XDP buffer
allocation API") this piece of code was moved into the new function called
xp_aligned_validate_desc(). This function was then moved into xsk_queue.h
via 26062b185eee ("xsk: Explicitly inline functions and move definitions").

Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Link: https://lore.kernel.org/bpf/20210428094424.54435-1-xuanzhuo@xxxxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/xdp/xsk_queue.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index ef6de0fb4e31..be9fd5a72011 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -126,13 +126,12 @@ static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
 static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
 					    struct xdp_desc *desc)
 {
-	u64 chunk, chunk_end;
+	u64 chunk;
 
-	chunk = xp_aligned_extract_addr(pool, desc->addr);
-	chunk_end = xp_aligned_extract_addr(pool, desc->addr + desc->len);
-	if (chunk != chunk_end)
+	if (desc->len > pool->chunk_size)
 		return false;
 
+	chunk = xp_aligned_extract_addr(pool, desc->addr);
 	if (chunk >= pool->addrs_cnt)
 		return false;
 
-- 
2.30.2