From: J. Bruce Fields Date: Mon, 22 Dec 2014 21:14:51 +0000 (-0500) Subject: rpc: fix xdr_truncate_encode to handle buffer ending on page boundary X-Git-Tag: v3.16.35~3129 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=520245221c103eb0589834d5afbc6d377154b842;p=thirdparty%2Fkernel%2Fstable.git rpc: fix xdr_truncate_encode to handle buffer ending on page boundary commit 49a068f82a1d30eb585d7804b05948376be6cf9a upstream. A struct xdr_stream at a page boundary might point to the end of one page or the beginning of the next, but xdr_truncate_encode isn't prepared to handle the former. This can cause corruption of NFSv4 READDIR replies in the case that a readdir entry that would have exceeded the client's dircount/maxcount limit would have ended exactly on a 4k page boundary. You're more likely to hit this case on large directories. Other xdr_truncate_encode callers are probably also affected. Reported-by: Holger Hoffstätte Tested-by: Holger Hoffstätte Fixes: 3e19ce762b53 "rpc: xdr_truncate_encode" Signed-off-by: J. Bruce Fields Signed-off-by: Luis Henriques --- diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 23fb4e75e2454..25ef792dfee68 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -605,7 +605,7 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len) struct kvec *head = buf->head; struct kvec *tail = buf->tail; int fraglen; - int new, old; + int new; if (len > buf->len) { WARN_ON_ONCE(1); @@ -627,8 +627,8 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len) buf->len -= fraglen; new = buf->page_base + buf->page_len; - old = new + fraglen; - xdr->page_ptr -= (old >> PAGE_SHIFT) - (new >> PAGE_SHIFT); + + xdr->page_ptr = buf->pages + (new >> PAGE_SHIFT); if (buf->page_len && buf->len == len) { xdr->p = page_address(*xdr->page_ptr);