From 3cc9a472d625f31f981063882b07e96229b9e71a Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Wed, 2 May 2018 13:50:19 -0700 Subject: [PATCH] bpf: sockmap, fix scatterlist update on error path in send with apply When the call to do_tcp_sendpage() fails to send the complete block requested we either retry if only a partial send was completed or abort if we receive a error less than or equal to zero. Before returning though we must update the scatterlist length/offset to account for any partial send completed. Before this patch we did this at the end of the retry loop, but this was buggy when used while applying a verdict to fewer bytes than in the scatterlist. When the scatterlist length was being set we forgot to account for the apply logic reducing the size variable. So the result was we chopped off some bytes in the scatterlist without doing proper cleanup on them. This results in a WARNING when the sock is tore down because the bytes have previously been charged to the socket but are never uncharged. The simple fix is to simply do the accounting inside the retry loop subtracting from the absolute scatterlist values rather than trying to accumulate the totals and subtract at the end. Reported-by: Alexei Starovoitov Signed-off-by: John Fastabend Signed-off-by: Alexei Starovoitov --- kernel/bpf/sockmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c index 634415c7fbcd..943929a05c92 100644 --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -326,6 +326,9 @@ retry: if (ret > 0) { if (apply) apply_bytes -= ret; + + sg->offset += ret; + sg->length -= ret; size -= ret; offset += ret; if (uncharge) @@ -333,8 +336,6 @@ retry: goto retry; } - sg->length = size; - sg->offset = offset; return ret; } -- 2.20.1