On Fri, 2 May 2025 at 06:04, Guang Yuan Wu <gwu@xxxxxxx> wrote: > > fuse: fix race between concurrent setattrs from multiple nodes > > 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@xxxxxxx> > Reviewed-by: Bernd Schubert <bschubert@xxxxxxx> Applied with minor modification (see fuse.git#for-next). Thanks. Miklos
