kernel/linux.git/fs/overlayfs/export.c, branch v6.12.80

ovl: support encoding fid from inode with no alias

2025-01-17T12:40:36+00:00

[ Upstream commit c45beebfde34aa71afbc48b2c54cdda623515037 ] Dmitry Safonov reported that a WARN_ON() assertion can be trigered by userspace when calling inotify_show_fdinfo() for an overlayfs watched inode, whose dentry aliases were discarded with drop_caches. The WARN_ON() assertion in inotify_show_fdinfo() was removed, because it is possible for encoding file handle to fail for other reason, but the impact of failing to encode an overlayfs file handle goes beyond this assertion. As shown in the LTP test case mentioned in the link below, failure to encode an overlayfs file handle from a non-aliased inode also leads to failure to report an fid with FAN_DELETE_SELF fanotify events. As Dmitry notes in his analyzis of the problem, ovl_encode_fh() fails if it cannot find an alias for the inode, but this failure can be fixed. ovl_encode_fh() seldom uses the alias and in the case of non-decodable file handles, as is often the case with fanotify fid info, ovl_encode_fh() never needs to use the alias to encode a file handle. Defer finding an alias until it is actually needed so ovl_encode_fh() will not fail in the common case of FAN_DELETE_SELF fanotify events. Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") Reported-by: Dmitry Safonov Closes: https://lore.kernel.org/linux-fsdevel/CAOQ4uxiie81voLZZi2zXS1BziXZCM24nXqPAxbu8kxXCUWdwOg@mail.gmail.com/ Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20250105162404.357058-3-amir73il@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

ovl: pass realinode to ovl_encode_real_fh() instead of realdentry

2025-01-17T12:40:36+00:00

[ Upstream commit 07aeefae7ff44d80524375253980b1bdee2396b0 ] We want to be able to encode an fid from an inode with no alias. Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20250105162404.357058-2-amir73il@gmail.com Signed-off-by: Christian Brauner Stable-dep-of: c45beebfde34 ("ovl: support encoding fid from inode with no alias") Signed-off-by: Sasha Levin

ovl: fix encoding fid for lower only root

2024-06-14T08:30:40+00:00

ovl_check_encode_origin() should return a positive number if the lower dentry is to be encoded, zero otherwise. If there's no upper layer at all (read-only overlay), then it obviously needs to return positive. This was broken by commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles"), which didn't take the lower-only configuration into account. Fix by checking the no-upper-layer case up-front. Reported-and-tested-by: Youzhong Yang Closes: https://lore.kernel.org/all/CADpNCvaBimi+zCYfRJHvCOhMih8OU0rmZkwLuh24MKKroRuT8Q@mail.gmail.com/ Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") Cc: # v6.6 Signed-off-by: Miklos Szeredi

Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-01-12T04:11:35+00:00

Pull dcache updates from Al Viro: "Change of locking rules for __dentry_kill(), regularized refcounting rules in that area, assorted cleanups and removal of weird corner cases (e.g. now ->d_iput() on child is always called before the parent might hit __dentry_kill(), etc)" * tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits) dcache: remove unnecessary NULL check in dget_dlock() kill DCACHE_MAY_FREE __d_unalias() doesn't use inode argument d_alloc_parallel(): in-lookup hash insertion doesn't need an RCU variant get rid of DCACHE_GENOCIDE d_genocide(): move the extern into fs/internal.h simple_fill_super(): don't bother with d_genocide() on failure nsfs: use d_make_root() d_alloc_pseudo(): move setting ->d_op there from the (sole) caller kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller retain_dentry(): introduce a trimmed-down lockless variant __dentry_kill(): new locking scheme d_prune_aliases(): use a shrink list switch select_collect{,2}() to use of to_shrink_list() to_shrink_list(): call only if refcount is 0 fold dentry_kill() into dput() don't try to cut corners in shrink_lock_dentry() fold the call of retain_dentry() into fast_dput() Call retain_dentry() with refcount 0 dentry_kill(): don't bother with retain_dentry() on slow path ...

ovl: remove redundant ofs->indexdir member

2023-11-20T07:49:09+00:00

When the index feature is disabled, ofs->indexdir is NULL. When the index feature is enabled, ofs->indexdir has the same value as ofs->workdir and takes an extra reference. This makes the code harder to understand when it is not always clear that ofs->indexdir in one function is the same dentry as ofs->workdir in another function. Remove this redundancy, by referencing ofs->workdir directly in index helpers and by using the ovl_indexdir() accessor in generic code. Signed-off-by: Amir Goldstein

ovl: stop using d_alloc_anon()/d_instantiate_anon()

2023-11-18T21:15:19+00:00

Commit f9c34674bc60 ("vfs: factor out helpers d_instantiate_anon() and d_alloc_anon()") was introduced so overlayfs could initialize a non-dir disconnected overlay dentry before overlay inode is attached to it. Since commit ("0af950f57fef ovl: move ovl_entry into ovl_inode"), all ovl_obtain_alias() can do is set DCACHE_OP_*REVALIDATE flags in ->d_flags and OVL_E_UPPER_ALIAS flag in ->d_fsdata. The DCACHE_OP_*REVALIDATE flags and OVL_E_UPPER_ALIAS flag are irrelevant for a disconnected non-dir dentry, so it is better to use d_obtain_alias() instead of open coding it. Suggested-by: Al Viro Signed-off-by: Amir Goldstein Signed-off-by: Al Viro

ovl: reorder ovl_want_write() after ovl_inode_lock()

2023-10-30T22:12:57+00:00

Make the locking order of ovl_inode_lock() strictly between the two vfs stacked layers, i.e.: - ovl vfs locks: sb_writers, inode_lock, ... - ovl_inode_lock - upper vfs locks: sb_writers, inode_lock, ... To that effect, move ovl_want_write() into the helpers ovl_nlink_start() and ovl_copy_up_start which currently take the ovl_inode_lock() after ovl_want_write(). Signed-off-by: Amir Goldstein

ovl: fix NULL pointer defer when encoding non-decodable lower fid

2023-10-03T06:24:11+00:00

A wrong return value from ovl_check_encode_origin() would cause ovl_dentry_to_fid() to try to encode fid from NULL upper dentry. Reported-by: syzbot+2208f82282740c1c8915@syzkaller.appspotmail.com Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") Signed-off-by: Amir Goldstein

ovl: make consistent use of OVL_FS()

2023-08-12T16:02:54+00:00

Always use OVL_FS() to retrieve the corresponding struct ovl_fs from a struct super_block. Reviewed-by: Amir Goldstein Signed-off-by: Andrea Righi Signed-off-by: Amir Goldstein

ovl: support encoding non-decodable file handles

2023-08-12T16:02:47+00:00

When all layers support file handles, we support encoding non-decodable file handles (a.k.a. fid) even with nfs_export=off. When file handles do not need to be decoded, we do not need to copy up redirected lower directories on encode, and we encode also non-indexed upper with lower file handle, so fid will not change on copy up. This enables reporting fanotify events with file handles on overlayfs with default config/mount options. Signed-off-by: Amir Goldstein