[PATCH] FUSE: serious information leak fix

[Miklos Szeredi]

In certain situations the user can read out previous contents of
pages.  To do this, create a filesystem that returns a short count on
a read request.  Then issue a read for a file.  If there are pages to
be read, that are not touched at all, these will not be zeroed.

The fix is to zero out all pages that are not touched.

Thanks to Sven Tantau for the bug report.

Signed-off-by: Miklos Szeredi <miklos@xxxxxxxxxx>

Index: linux/fs/fuse/dev.c
===================================================================
--- linux.orig/fs/fuse/dev.c	2005-06-01 12:22:08.000000000 +0200
+++ linux/fs/fuse/dev.c	2005-06-02 11:10:08.000000000 +0200
@@ -525,7 +525,7 @@ static int fuse_copy_pages(struct fuse_c
 	unsigned offset = req->page_offset;
 	unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);
 
-	for (i = 0; i < req->num_pages && nbytes; i++) {
+	for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
 		struct page *page = req->pages[i];
 		int err = fuse_copy_page(cs, page, offset, count, zeroing);
 		if (err)
-
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