On Thu, 2022-06-30 at 13:24 -0400, Chuck Lever wrote: > Looks like there are still cases when "space_left - frag1bytes" can > legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains > within the current encode buffer. > > Reported-by: Bruce Fields <bfields@xxxxxxxxxxxx> > Reported-by: Zorro Lang <zlang@xxxxxxxxxx> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151 > Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in > xdr_get_next_encode_buffer()") > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > --- > net/sunrpc/xdr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Hi- > > I had a few minutes yesterday afternoon to look into this one. The > following one-liner seems to address the issue and passes my smoke > tests with NFSv4.1/TCP and NFSv3/RDMA. Any thoughts? > > > diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c > index f87a2d8f23a7..916659be2774 100644 > --- a/net/sunrpc/xdr.c > +++ b/net/sunrpc/xdr.c > @@ -987,7 +987,7 @@ static noinline __be32 > *xdr_get_next_encode_buffer(struct xdr_stream *xdr, > if (space_left - nbytes >= PAGE_SIZE) > xdr->end = p + PAGE_SIZE; > else > - xdr->end = p + space_left - frag1bytes; > + xdr->end = p + min_t(int, space_left - frag1bytes, > PAGE_SIZE); Since we know that frag1bytes <= nbytes (that is determined in xdr_reserve_space()), isn't this effectively the same thing as changing the condition to if (space_left - frag1bytes >= PAGE_SIZE) xdr->end = p + PAGE_SIZE; else xdr->end = p + space_left - frag1bytes; ? > > xdr->buf->page_len += frag2bytes; > xdr->buf->len += nbytes; > > -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
