6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Guang Yuan Wu gwu@ddn.com
[ Upstream commit 69efbff69f89c9b2b72c4d82ad8b59706add768a ]
When mounting a user-space filesystem on multiple clients, after concurrent ->setattr() calls from different node, stale inode attributes may be cached in some node.
This is caused by fuse_setattr() racing with fuse_reverse_inval_inode().
When filesystem server receives setattr request, the client node with valid iattr cached will be required to update the fuse_inode's attr_version and invalidate the cache by fuse_reverse_inval_inode(), and at the next call to ->getattr() they will be fetched from user space.
The race scenario is: 1. client-1 sends setattr (iattr-1) request to server 2. client-1 receives the reply from server 3. before client-1 updates iattr-1 to the cached attributes by fuse_change_attributes_common(), server receives another setattr (iattr-2) request from client-2 4. server requests client-1 to update the inode attr_version and invalidate the cached iattr, and iattr-1 becomes staled 5. client-2 receives the reply from server, and caches iattr-2 6. continue with step 2, client-1 invokes fuse_change_attributes_common(), and caches iattr-1
The issue has been observed from concurrent of chmod, chown, or truncate, which all invoke ->setattr() call.
The solution is to use fuse_inode's attr_version to check whether the attributes have been modified during the setattr request's lifetime. If so, mark the attributes as invalid in the function fuse_change_attributes_common().
Signed-off-by: Guang Yuan Wu gwu@ddn.com Reviewed-by: Bernd Schubert bschubert@ddn.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/fuse/dir.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 83ac192e7fdd1..fa90309030e21 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1946,6 +1946,7 @@ int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry, int err; bool trust_local_cmtime = is_wb; bool fault_blocked = false; + u64 attr_version;
if (!fc->default_permissions) attr->ia_valid |= ATTR_FORCE; @@ -2030,6 +2031,8 @@ int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry, if (fc->handle_killpriv_v2 && !capable(CAP_FSETID)) inarg.valid |= FATTR_KILL_SUIDGID; } + + attr_version = fuse_get_attr_version(fm->fc); fuse_setattr_fill(fc, &args, inode, &inarg, &outarg); err = fuse_simple_request(fm, &args); if (err) { @@ -2055,6 +2058,14 @@ int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry, /* FIXME: clear I_DIRTY_SYNC? */ }
+ if (fi->attr_version > attr_version) { + /* + * Apply attributes, for example for fsnotify_change(), but set + * attribute timeout to zero. + */ + outarg.attr_valid = outarg.attr_valid_nsec = 0; + } + fuse_change_attributes_common(inode, &outarg.attr, NULL, ATTR_TIMEOUT(&outarg), fuse_get_cache_mask(inode), 0);