Commit 67fad106 authored Dec 12, 2012 by Jeff Layton Committed by Trond Myklebust Dec 12, 2012

nfs: don't zero out the rest of the page if we hit the EOF on a DIO READ



Eryu provided a test program that would segfault when attempting to read
past the EOF on file that was opened O_DIRECT. The buffer given to the
read() call was on the stack, and when he attempted to read past it it
would scribble over the rest of the stack page.

If we hit the end of the file on a DIO READ request, then we don't want
to zero out the rest of the buffer. These aren't pagecache pages after
all, and there's no guarantee that the buffers that were passed in
represent entire pages.

Cc: <stable@vger.kernel.org> # v3.5+
Cc: Fred Isaman <iisaman@netapp.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

parent b0ef9647

fs/nfs/direct.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -266,14 +266,6 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
		struct page *page = req->wb_page;

		if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
		if (bytes > hdr->good_bytes)
		zero_user(page, 0, PAGE_SIZE);
		else if (hdr->good_bytes - bytes < PAGE_SIZE)
		zero_user_segment(page,
		hdr->good_bytes & ~PAGE_MASK,
		PAGE_SIZE);
		}
		if (!PageCompound(page)) {
		if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
		if (bytes < hdr->good_bytes)

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