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sunrpc: Avoid a KASAN slab-out-of-bounds bug in xdr_set_page_base()

This seems to happen fairly easily during READ_PLUS testing on NFS v4.2.
I found that we could end up accessing xdr->buf->pages[pgnr] with a pgnr
greater than the number of pages in the array. So let's just return
early if we're setting base to a point at the end of the page data and
let xdr_set_tail_base() handle setting up the buffer pointers instead.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Fixes: 8d86e373b0 ("SUNRPC: Clean up helpers xdr_set_iov() and xdr_set_page_base()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Anna Schumaker 2021-06-09 17:07:29 -04:00 committed by Trond Myklebust
parent 3731d44bba
commit 6d1c0f3d28

View file

@ -1230,10 +1230,9 @@ static unsigned int xdr_set_page_base(struct xdr_stream *xdr,
void *kaddr;
maxlen = xdr->buf->page_len;
if (base >= maxlen) {
base = maxlen;
maxlen = 0;
} else
if (base >= maxlen)
return 0;
else
maxlen -= base;
if (len > maxlen)
len = maxlen;