On Thu, Jun 30, 2022 at 2:09 PM Anna Schumaker <schumaker.anna@xxxxxxxxx> wrote: > > On Thu, Jun 30, 2022 at 2:03 PM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > 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; > > I added some printk's without this patch, and I'm seeing space_left > larger than PAGE_SIZE and frag1bytes set to 0 in that branch right > before the crash. So the min_t() will choose the PAGE_SIZE option > sometimes. Actually, ignore me. I initially misread what Trond said. After a reread I saw he changed "space_left - nbytes" to "space_left - frag1bytes" in the if condition. Trond's way fixes the crash for me, too. Anna > > Anna > > > > > ? > > > > > > xdr->buf->page_len += frag2bytes; > > > xdr->buf->len += nbytes; > > > > > > > > > > -- > > Trond Myklebust > > Linux NFS client maintainer, Hammerspace > > trond.myklebust@xxxxxxxxxxxxxxx > > > >
