linux-kernel - [PATCH v2 02/25] cachefiles: Fix non-taking of sb

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Message-ID: <20240814203850.2240469-3-dhowells@redhat.com>
Date: Wed, 14 Aug 2024 21:38:22 +0100
From: David Howells <dhowells@...hat.com>
To: Christian Brauner <christian@...uner.io>,
	Steve French <smfrench@...il.com>,
	Matthew Wilcox <willy@...radead.org>
Cc: David Howells <dhowells@...hat.com>,
	Jeff Layton <jlayton@...nel.org>,
	Gao Xiang <hsiangkao@...ux.alibaba.com>,
	Dominique Martinet <asmadeus@...ewreck.org>,
	Marc Dionne <marc.dionne@...istor.com>,
	Paulo Alcantara <pc@...guebit.com>,
	Shyam Prasad N <sprasad@...rosoft.com>,
	Tom Talpey <tom@...pey.com>,
	Eric Van Hensbergen <ericvh@...nel.org>,
	Ilya Dryomov <idryomov@...il.com>,
	netfs@...ts.linux.dev,
	linux-afs@...ts.infradead.org,
	linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	ceph-devel@...r.kernel.org,
	v9fs@...ts.linux.dev,
	linux-erofs@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Christian Brauner <brauner@...nel.org>,
	Gao Xiang <xiang@...nel.org>
Subject: [PATCH v2 02/25] cachefiles: Fix non-taking of sb_writers around set/removexattr

Unlike other vfs_xxxx() calls, vfs_setxattr() and vfs_removexattr() don't
take the sb_writers lock, so the caller should do it for them.

Fix cachefiles to do this.

Fixes: 9ae326a69004 ("CacheFiles: A cache that backs onto a mounted filesystem")
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Christian Brauner <brauner@...nel.org>
cc: Gao Xiang <xiang@...nel.org>
cc: netfs@...ts.linux.dev
cc: linux-erofs@...ts.ozlabs.org
cc: linux-fsdevel@...r.kernel.org
---
 fs/cachefiles/xattr.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index 4dd8a993c60a..7c6f260a3be5 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -64,9 +64,15 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object)
 		memcpy(buf->data, fscache_get_aux(object->cookie), len);
 
 	ret = cachefiles_inject_write_error();
-	if (ret == 0)
-		ret = vfs_setxattr(&nop_mnt_idmap, dentry, cachefiles_xattr_cache,
-				   buf, sizeof(struct cachefiles_xattr) + len, 0);
+	if (ret == 0) {
+		ret = mnt_want_write_file(file);
+		if (ret == 0) {
+			ret = vfs_setxattr(&nop_mnt_idmap, dentry,
+					   cachefiles_xattr_cache, buf,
+					   sizeof(struct cachefiles_xattr) + len, 0);
+			mnt_drop_write_file(file);
+		}
+	}
 	if (ret < 0) {
 		trace_cachefiles_vfs_error(object, file_inode(file), ret,
 					   cachefiles_trace_setxattr_error);
@@ -151,8 +157,14 @@ int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 	int ret;
 
 	ret = cachefiles_inject_remove_error();
-	if (ret == 0)
-		ret = vfs_removexattr(&nop_mnt_idmap, dentry, cachefiles_xattr_cache);
+	if (ret == 0) {
+		ret = mnt_want_write(cache->mnt);
+		if (ret == 0) {
+			ret = vfs_removexattr(&nop_mnt_idmap, dentry,
+					      cachefiles_xattr_cache);
+			mnt_drop_write(cache->mnt);
+		}
+	}
 	if (ret < 0) {
 		trace_cachefiles_vfs_error(object, d_inode(dentry), ret,
 					   cachefiles_trace_remxattr_error);
@@ -208,9 +220,15 @@ bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
 	memcpy(buf->data, p, volume->vcookie->coherency_len);
 
 	ret = cachefiles_inject_write_error();
-	if (ret == 0)
-		ret = vfs_setxattr(&nop_mnt_idmap, dentry, cachefiles_xattr_cache,
-				   buf, len, 0);
+	if (ret == 0) {
+		ret = mnt_want_write(volume->cache->mnt);
+		if (ret == 0) {
+			ret = vfs_setxattr(&nop_mnt_idmap, dentry,
+					   cachefiles_xattr_cache,
+					   buf, len, 0);
+			mnt_drop_write(volume->cache->mnt);
+		}
+	}
 	if (ret < 0) {
 		trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,
 					   cachefiles_trace_setxattr_error);