linux-kernel - [PATCH 4.17 041/220] fuse: atomic_o

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20180701160910.043200363@linuxfoundation.org>
Date:   Sun,  1 Jul 2018 18:21:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chad Austin <chadaustin@...com>,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 4.17 041/220] fuse: atomic_o_trunc should truncate pagecache

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@...hat.com>

commit df0e91d488276086bc07da2e389986cae0048c37 upstream.

Fuse has an "atomic_o_trunc" mode, where userspace filesystem uses the
O_TRUNC flag in the OPEN request to truncate the file atomically with the
open.

In this mode there's no need to send a SETATTR request to userspace after
the open, so fuse_do_setattr() checks this mode and returns.  But this
misses the important step of truncating the pagecache.

Add the missing parts of truncation to the ATTR_OPEN branch.

Reported-by: Chad Austin <chadaustin@...com>
Fixes: 6ff958edbf39 ("fuse: add atomic open+truncate support")
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/fuse/dir.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1629,8 +1629,19 @@ int fuse_do_setattr(struct dentry *dentr
 		return err;
 
 	if (attr->ia_valid & ATTR_OPEN) {
-		if (fc->atomic_o_trunc)
+		/* This is coming from open(..., ... | O_TRUNC); */
+		WARN_ON(!(attr->ia_valid & ATTR_SIZE));
+		WARN_ON(attr->ia_size != 0);
+		if (fc->atomic_o_trunc) {
+			/*
+			 * No need to send request to userspace, since actual
+			 * truncation has already been done by OPEN.  But still
+			 * need to truncate page cache.
+			 */
+			i_size_write(inode, 0);
+			truncate_pagecache(inode, 0);
 			return 0;
+		}
 		file = NULL;
 	}