[ 048/108] svcrpc: fix BUG() in svc_tcp_clear_pages

From: Greg Kroah-Hartman
Date: Wed Sep 12 2012 - 19:32:29 EST

From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>

3.5-stable review patch. If anyone has any objections, please let me know.


From: "J. Bruce Fields" <bfields@xxxxxxxxxx>

commit be1e44441a560c43c136a562d49a1c9623c91197 upstream.

Examination of svc_tcp_clear_pages shows that it assumes sk_tcplen is
consistent with sk_pages[] (in particular, sk_pages[n] can't be NULL if
sk_tcplen would lead us to expect n pages of data).

svc_tcp_restore_pages zeroes out sk_pages[] while leaving sk_tcplen.
This is OK, since both functions are serialized by XPT_BUSY. However,
that means the inconsistency must be repaired before dropping XPT_BUSY.

Therefore we should be ensuring that svc_tcp_save_pages repairs the
problem before exiting svc_tcp_recv_record on error.

Symptoms were a BUG() in svc_tcp_clear_pages.

Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

net/sunrpc/svcsock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1129,9 +1129,9 @@ static int svc_tcp_recvfrom(struct svc_r
if (len >= 0)
svsk->sk_tcplen += len;
if (len != want) {
+ svc_tcp_save_pages(svsk, rqstp);
if (len < 0 && len != -EAGAIN)
goto err_other;
- svc_tcp_save_pages(svsk, rqstp);
dprintk("svc: incomplete TCP record (%d of %d)\n",
svsk->sk_tcplen, svsk->sk_reclen);
goto err_noclose;

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