fuse: mark all aliases of an inode stale in unlink
Subsystems (2)
PATCH 1/1 fuse: mark all aliases of an inode stale in unlink
Problem:
create("filename") => 0
link("filename", "linkname") => 0
unlink("filename") => 0
link("linkname", "filename") => -ENOENT ### BUG ###This is a test case link section of the Poix compliance test suite from ntfs-3g project.
Cause:
fuse_unlink() clears i_nlink of the inode. If the inode has
hardlinks (and hence aliases) they kept fresh (within the entry timeout bounds.) A link() call happening right after unlink now checks for i_nlink == 0 (since patch aae8a97d3ec30788790d1720b71d76fd8eb44b73) and fails the syscall for security reasons.
Fix:
Instead of marking the just-unlinked entry as stale, mark all
the aliases as stale so that a revalidation of the alias is done during path resolution.
Signed-off-by Anand Avati <[email protected]>
--- fs/fuse/dir.c | 21 ++++++++++++++++++++- 1 files changed, 20 insertions(+), 1 deletions(-)
fs/fuse/dir.c +20 -1
@@ -103,6 +103,25 @@ void fuse_invalidate_entry_cache(struct dentry *entry) }/* +* Mark all dentry aliases of an inode as stale. It is necessary to mark +* all aliases as stale because a link() on an inode performed right +* after an unlink on one of the hardlinks will pick the inode without +* a revalidate and find i_nlink == 0. This ends up getting checked as +* a security vulnerability and fail -ENOENT. Marking all aliases as stale +* will instead force lookup the inode freshly at the time of link() +*/ +void fuse_invalidate_all_aliases (struct inode *inode) +{ +struct dentry *alias; + +spin_lock (&inode->i_lock); +list_for_each_entry (alias, &inode->i_dentry, d_alias) { +fuse_invalidate_entry_cache (alias); + } +spin_unlock (&inode->i_lock); +} + +/* * Same as fuse_invalidate_entry_cache(), but also try to remove the * dentry from the hash */
@@ -653,7 +672,7 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)clear_nlink (inode);fuse_invalidate_attr (inode);fuse_invalidate_attr (dir); -fuse_invalidate_entry_cache (entry); +fuse_invalidate_all_aliases (inode); }else if (err == -EINTR )fuse_invalidate_entry (entry);return err;
Signature · 10 lines
1.7.6.4 -- "It's easier said than done." ... and if you don't believe it, try proving that it's easier done than said, and you'll see that "it's easier said that `it's easier done than said' than it is done", which really proves that "it's easier said than done".