The root inode has a fixed nodeid and generation (1, 0).
Prior to the commit 15db16837a35 ("fuse: fix illegal access to inode with reused nodeid") generation number on lookup was ignored. After this commit lookup with the wrong generation number resulted in the inode being unhashed. This is correct for non-root inodes, but replacing the root inode is wrong and results in weird behavior.
Fix by reverting to the old behavior if ignoring the generation for the root inode, but issuing a warning in dmesg.
Reported-by: Antonio SJ Musumeci trapexit@spawn.link Closes: https://lore.kernel.org/all/CAOQ4uxhek5ytdN8Yz2tNEOg5ea4NkBb4nk0FGPjPk_9nz-V... Fixes: 15db16837a35 ("fuse: fix illegal access to inode with reused nodeid") Cc: stable@vger.kernel.org # v5.14 Signed-off-by: Miklos Szeredi mszeredi@redhat.com --- fs/fuse/dir.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index ce6a38c56d54..befb7dfe387a 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -391,6 +391,10 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name err = -EIO; if (fuse_invalid_attr(&outarg->attr)) goto out_put_forget; + if (outarg->nodeid == FUSE_ROOT_ID && outarg->generation != 0) { + pr_warn_once("root generation should be zero\n"); + outarg->generation = 0; + }
*inode = fuse_iget(sb, outarg->nodeid, outarg->generation, &outarg->attr, ATTR_TIMEOUT(outarg),