| Message ID | 20201204183419.1532347-1-dan@kernelim.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | sunrpc: fix xs_read_xdr_buf for partial pages receive | expand |
On Fri, 2020-12-04 at 20:34 +0200, Dan Aloni wrote: > When receiving pages data, return value 'ret' when positive includes > `buf->page_base`, so we should subtract it similarly to how it is > done > for `offset`. > > This was discovered on the very rare cases where the server returned > a > chunk of bytes that when added to the already received amount of > bytes > for the pages happened to match the current `recv.len`, for example > on this case: > > buf->page_base : 258356 > actually received from socket: 1740 > ret : 260096 > want : 260096 > > In this case neither of the two 'if ... goto out' trigger, and we > continue to tail parsing. > > Worth to mention that the ensuing EMSGSIZE from the continued > execution of > `xs_read_xdr_buf` may be observed by an application due to 4 > superfluous > bytes being added to the pages data. > > Fixes: 277e4ab7d53 ("SUNRPC: Simplify TCP receive code by switching > to > using iterators") > Signed-off-by: Dan Aloni <dan@kernelim.com> > --- > net/sunrpc/xprtsock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > index 7090bbee0ec5..42b680a60d38 100644 > --- a/net/sunrpc/xprtsock.c > +++ b/net/sunrpc/xprtsock.c > @@ -436,7 +436,7 @@ xs_read_xdr_buf(struct socket *sock, struct > msghdr *msg, int flags, > offset += ret - buf->page_base; > if (offset == count || msg->msg_flags & > (MSG_EOR|MSG_TRUNC)) > goto out; > - if (ret != want) > + if (ret - buf->page_base != want) > goto out; > seek = 0; > } else { Ouch... Well spotted! Hmm... I think we want to just subtract out the buf->page_base from the value of 'ret' after we call xs_flush_bvec() and then adjust the calculation of 'offset' in the next line. That's more efficient. Can you please resend with that change?
On Fri, Dec 04, 2020 at 08:52:55PM +0000, Trond Myklebust wrote: > On Fri, 2020-12-04 at 20:34 +0200, Dan Aloni wrote: [..] > > --- a/net/sunrpc/xprtsock.c > > +++ b/net/sunrpc/xprtsock.c > > @@ -436,7 +436,7 @@ xs_read_xdr_buf(struct socket *sock, struct > > msghdr *msg, int flags, > > offset += ret - buf->page_base; > > if (offset == count || msg->msg_flags & > > (MSG_EOR|MSG_TRUNC)) > > goto out; > > - if (ret != want) > > + if (ret - buf->page_base != want) > > goto out; > > seek = 0; > > } else { > > Ouch... Well spotted! > > Hmm... I think we want to just subtract out the buf->page_base from the > value of 'ret' after we call xs_flush_bvec() and then adjust the > calculation of 'offset' in the next line. That's more efficient. Yes, it works out, though after being aware that the positive value of `ret` when returned from `xs_read_xdr_buf` and propagated upward has no effect except on traces.
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 7090bbee0ec5..42b680a60d38 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -436,7 +436,7 @@ xs_read_xdr_buf(struct socket *sock, struct msghdr *msg, int flags, offset += ret - buf->page_base; if (offset == count || msg->msg_flags & (MSG_EOR|MSG_TRUNC)) goto out; - if (ret != want) + if (ret - buf->page_base != want) goto out; seek = 0; } else {
When receiving pages data, return value 'ret' when positive includes `buf->page_base`, so we should subtract it similarly to how it is done for `offset`. This was discovered on the very rare cases where the server returned a chunk of bytes that when added to the already received amount of bytes for the pages happened to match the current `recv.len`, for example on this case: buf->page_base : 258356 actually received from socket: 1740 ret : 260096 want : 260096 In this case neither of the two 'if ... goto out' trigger, and we continue to tail parsing. Worth to mention that the ensuing EMSGSIZE from the continued execution of `xs_read_xdr_buf` may be observed by an application due to 4 superfluous bytes being added to the pages data. Fixes: 277e4ab7d53 ("SUNRPC: Simplify TCP receive code by switching to using iterators") Signed-off-by: Dan Aloni <dan@kernelim.com> --- net/sunrpc/xprtsock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)