[PATCH bpf v2] xsk: fix for xp_aligned_validate_desc() when len == chunk_size

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

Related commit:
commit 2b43470add8c ("xsk: Introduce AF_XDP buffer allocation API")
commit 26062b185eee ("xsk: Explicitly inline functions and move
                    definitions")

This problem was first introduced in "bbff2f321a86". Later in
"2b43470add8c" this piece of code was moved into the new function
xp_aligned_validate_desc(). Later this function was moved into the file
xsk_queue.h in "26062b185eee".

Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 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 2823b7c3302d..40f359bf2044 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h

@@ -128,13 +128,12 @@ 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;
 

-- 
2.31.0

Hello:

This patch was applied to bpf/bpf.git (refs/heads/master):

On Wed, 28 Apr 2021 17:44:24 +0800 you wrote:

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

Related commit:
commit 2b43470add8c ("xsk: Introduce AF_XDP buffer allocation API")
commit 26062b185eee ("xsk: Explicitly inline functions and move
                    definitions")

[...]

Here is the summary with links:
  - [bpf,v2] xsk: fix for xp_aligned_validate_desc() when len == chunk_size
    https://git.kernel.org/bpf/bpf/c/ac31565c2193

You are awesome, thank you!
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