linux-kernel - [PATCH] fuse: initialize attr_version of new fuse inodes by fc->attr

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Date:   Fri, 11 Nov 2022 17:37:02 +0800
From:   Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
Subject: [PATCH] fuse: initialize attr_version of new fuse inodes by fc->attr_version

The FUSE_READDIRPLUS request reply handler fuse_direntplus_link() might
call fuse_iget() to initialize a new fuse_inode and change its attributes.
But as the new fi->attr_version is always initialized with 0, even if the
attr_version of the FUSE_READDIRPLUS request has become staled, staled attr
may still be set to the new fuse_inode. This may cause file size
inconsistency even when a filesystem backend is mounted with a single FUSE
mountpoint.

This commit fixes the issue by initializing new fuse_inode attr_versions by
the global fc->attr_version. This may introduce more FUSE_GETATTR but can
avoid weird attributes rollback being seen by users.

Fixes: 19332138887c ("fuse: initialize attr_version of new fuse inodes by fc->attr_version")
Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
---
 fs/fuse/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6b3beda16c1b..145ded6b55af 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -71,6 +71,7 @@ struct fuse_forget_link *fuse_alloc_forget(void)
 static struct inode *fuse_alloc_inode(struct super_block *sb)
 {
 	struct fuse_inode *fi;
+	struct fuse_conn *fc = get_fuse_conn_super(sb);

 	fi = alloc_inode_sb(sb, fuse_inode_cachep, GFP_KERNEL);
 	if (!fi)
@@ -80,7 +81,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	fi->inval_mask = 0;
 	fi->nodeid = 0;
 	fi->nlookup = 0;
-	fi->attr_version = 0;
+	fi->attr_version = fuse_get_attr_version(fc);
 	fi->orig_ino = 0;
 	fi->state = 0;
 	mutex_init(&fi->mutex);
-- 
2.20.1