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It's caused by io_zcrx_recv_skb() adjusting desc->count for all received buffers including frag lists, but then doing recursive calls to process frag list skbs, which leads to desc->count double accounting and underflow. Reported-and-tested-by: Matthias Jasny Fixes: 6699ec9a23f85 ("io_uring/zcrx: add a read limit to recvzc requests") Cc: stable@vger.kernel.org Signed-off-by: Pavel Begunkov --- io_uring/zcrx.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c index 723e4266b91f..ef73440b605a 100644 --- a/io_uring/zcrx.c +++ b/io_uring/zcrx.c @@ -1236,12 +1236,16 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct sk_buff *skb, end = start + frag_iter->len; if (offset < end) { + size_t count; + copy = end - offset; if (copy > len) copy = len; off = offset - start; + count = desc->count; ret = io_zcrx_recv_skb(desc, frag_iter, off, copy); + desc->count = count; if (ret < 0) goto out; -- 2.49.0