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| author | NeilBrown <neil@brown.name> | 2025-03-19 14:01:35 +1100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-04-08 11:24:36 +0200 |
| commit | fa6fe07d1536361a227d655e69ca270faf28fdbe (patch) | |
| tree | 55e12a65d8b5f39c930aa14ae1342e6cacdfa4e8 /Documentation/filesystems | |
| parent | 2011067c6477b55ef510e4ef830bca2869cd8136 (diff) | |
| download | tip-fa6fe07d1536361a227d655e69ca270faf28fdbe.tar.gz | |
VFS: rename lookup_one_len family to lookup_noperm and remove permission check
The lookup_one_len family of functions is (now) only used internally by
a filesystem on itself either
- in a context where permission checking is irrelevant such as by a
virtual filesystem populating itself, or xfs accessing its ORPHANAGE
or dquota accessing the quota file; or
- in a context where a permission check (MAY_EXEC on the parent) has just
been performed such as a network filesystem finding in "silly-rename"
file in the same directory. This is also the context after the
_parentat() functions where currently lookup_one_qstr_excl() is used.
So the permission check is pointless.
The name "one_len" is unhelpful in understanding the purpose of these
functions and should be changed. Most of the callers pass the len as
"strlen()" so using a qstr and QSTR() can simplify the code.
This patch renames these functions (include lookup_positive_unlocked()
which is part of the family despite the name) to have a name based on
"lookup_noperm". They are changed to receive a 'struct qstr' instead
of separate name and len. In a few cases the use of QSTR() results in a
new call to strlen().
try_lookup_noperm() takes a pointer to a qstr instead of the whole
qstr. This is consistent with d_hash_and_lookup() (which is nearly
identical) and useful for lookup_noperm_unlocked().
The new lookup_noperm_common() doesn't take a qstr yet. That will be
tidied up in a subsequent patch.
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/porting.rst | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 57dcba6de7434f..9150de7f64f142 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -1212,3 +1212,23 @@ lookup_one(), lookup_one_unlocked(), lookup_one_positive_unlocked() now take a qstr instead of a name and len. These, not the "one_len" versions, should be used whenever accessing a filesystem from outside that filesysmtem, through a mount point - which will have a mnt_idmap. + +--- + +** mandatory** + +Functions try_lookup_one_len(), lookup_one_len(), +lookup_one_len_unlocked() and lookup_positive_unlocked() have been +renamed to try_lookup_noperm(), lookup_noperm(), +lookup_noperm_unlocked(), lookup_noperm_positive_unlocked(). They now +take a qstr instead of separate name and length. QSTR() can be used +when strlen() is needed for the length. + +For try_lookup_noperm() a reference to the qstr is passed in case the +hash might subsequently be needed. + +These function no longer do any permission checking - they previously +checked that the caller has 'X' permission on the parent. They must +ONLY be used internally by a filesystem on itself when it knows that +permissions are irrelevant or in a context where permission checks have +already been performed such as after vfs_path_parent_lookup() |