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* [PATCH bpf v2] xsk: fix for xp_aligned_validate_desc() when len == chunk_size
@ 2021-04-28  9:44 Xuan Zhuo
  2021-05-03 22:40 ` patchwork-bot+netdevbpf
  0 siblings, 1 reply; 2+ messages in thread
From: Xuan Zhuo @ 2021-04-28  9:44 UTC (permalink / raw)
  To: bpf
  Cc: Björn Töpel, Magnus Karlsson, Jonathan Lemon,
	David S. Miller, Jakub Kicinski, Alexei Starovoitov,
	Daniel Borkmann, Jesper Dangaard Brouer, John Fastabend,
	Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
	KP Singh, netdev

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


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2021-04-28  9:44 [PATCH bpf v2] xsk: fix for xp_aligned_validate_desc() when len == chunk_size Xuan Zhuo
2021-05-03 22:40 ` patchwork-bot+netdevbpf

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