From: Amir Goldstein amir73il@gmail.com
commit 15db16837a35d8007cb8563358787412213db25e upstream.
Server responds to LOOKUP and other ops (READDIRPLUS/CREATE/MKNOD/...) with ourarg containing nodeid and generation.
If a fuse inode is found in inode cache with the same nodeid but different generation, the existing fuse inode should be unhashed and marked "bad" and a new inode with the new generation should be hashed instead.
This can happen, for example, with passhrough fuse filesystem that returns the real filesystem ino/generation on lookup and where real inode numbers can get recycled due to real files being unlinked not via the fuse passthrough filesystem.
With current code, this situation will not be detected and an old fuse dentry that used to point to an older generation real inode, can be used to access a completely new inode, which should be accessed only via the new dentry.
Note that because the FORGET message carries the nodeid w/o generation, the server should wait to get FORGET counts for the nlookup counts of the old and reused inodes combined, before it can free the resources associated to that nodeid.
Stable backport notes: * This is not a regression. The bug has been in fuse forever, but only a certain class of low level fuse filesystems can trigger this bug * Because there is no way to check if this fix is applied in runtime, libfuse test_examples.py tests this fix with hardcoded check for kernel version >= 5.14 * After backport to stable kernel(s), the libfuse test can be updated to also check minimal stable kernel version(s) * Depends on "fuse: fix bad inode" which is already applied to stable kernels v5.4.y and v5.10.y * Required backporting helper inode_wrong_type()
Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-fsdevel/CAOQ4uxi8DymG=JO_sAU+wS8akFdzh+PuXwW3E... Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fuse/dir.c | 2 +- fs/fuse/fuse_i.h | 7 +++++++ fs/fuse/inode.c | 4 ++-- fs/fuse/readdir.c | 7 +++++-- 4 files changed, 15 insertions(+), 5 deletions(-)
--- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -252,7 +252,7 @@ static int fuse_dentry_revalidate(struct if (ret == -ENOMEM) goto out; if (ret || fuse_invalid_attr(&outarg.attr) || - inode_wrong_type(inode, outarg.attr.mode)) + fuse_stale_inode(inode, outarg.generation, &outarg.attr)) goto invalid;
forget_all_cached_acls(inode); --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -860,6 +860,13 @@ static inline u64 fuse_get_attr_version( return atomic64_read(&fc->attr_version); }
+static inline bool fuse_stale_inode(const struct inode *inode, int generation, + struct fuse_attr *attr) +{ + return inode->i_generation != generation || + inode_wrong_type(inode, attr->mode); +} + static inline void fuse_make_bad(struct inode *inode) { remove_inode_hash(inode); --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -340,8 +340,8 @@ retry: inode->i_generation = generation; fuse_init_inode(inode, attr); unlock_new_inode(inode); - } else if (inode_wrong_type(inode, attr->mode)) { - /* Inode has changed type, any I/O on the old should fail */ + } else if (fuse_stale_inode(inode, generation, attr)) { + /* nodeid was reused, any I/O on the old inode should fail */ fuse_make_bad(inode); iput(inode); goto retry; --- a/fs/fuse/readdir.c +++ b/fs/fuse/readdir.c @@ -200,9 +200,12 @@ retry: if (!d_in_lookup(dentry)) { struct fuse_inode *fi; inode = d_inode(dentry); + if (inode && get_node_id(inode) != o->nodeid) + inode = NULL; if (!inode || - get_node_id(inode) != o->nodeid || - inode_wrong_type(inode, o->attr.mode)) { + fuse_stale_inode(inode, o->generation, &o->attr)) { + if (inode) + fuse_make_bad(inode); d_invalidate(dentry); dput(dentry); goto retry;