From: Aleksa Sarai <cyphar@cyphar•com>
To: Al Viro <viro@zeniv•linux.org.uk>,
Jeff Layton <jlayton@kernel•org>,
"J. Bruce Fields" <bfields@fieldses•org>,
Arnd Bergmann <arnd@arndb•de>,
David Howells <dhowells@redhat•com>,
Shuah Khan <shuah@kernel•org>,
Shuah Khan <skhan@linuxfoundation•org>,
Ingo Molnar <mingo@redhat•com>,
Peter Zijlstra <peterz@infradead•org>
Cc: linux-ia64@vger•kernel.org, linux-sh@vger•kernel.org,
Alexander Shishkin <alexander.shishkin@linux•intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes•dk>,
Alexei Starovoitov <ast@kernel•org>,
linux-kernel@vger•kernel.org, linux-kselftest@vger•kernel.org,
sparclinux@vger•kernel.org, Jiri Olsa <jolsa@redhat•com>,
linux-arch@vger•kernel.org, linux-s390@vger•kernel.org,
Tycho Andersen <tycho@tycho•ws>, Aleksa Sarai <asarai@suse•de>,
linux-arm-kernel@lists•infradead.org, linux-mips@vger•kernel.org,
linux-xtensa@linux-xtensa•org, Kees Cook <keescook@chromium•org>,
Jann Horn <jannh@google•com>,
linuxppc-dev@lists•ozlabs.org, Aleksa Sarai <cyphar@cyphar•com>,
Andy Lutomirski <luto@kernel•org>,
Namhyung Kim <namhyung@kernel•org>,
David Drysdale <drysdale@google•com>,
Christian Brauner <christian@brauner•io>,
libc-alpha@sourceware•org, linux-parisc@vger•kernel.org,
linux-m68k@lists•linux-m68k.org, linux-api@vger•kernel.org,
Chanho Min <chanho.min@lge•com>, Oleg Nesterov <oleg@redhat•com>,
Eric Biederman <ebiederm@xmission•com>,
linux-alpha@vger•kernel.org, linux-fsdevel@vger•kernel.org,
Andrew Morton <akpm@linux-foundation•org>,
Linus Torvalds <torvalds@linux-foundation•org>,
containers@lists•linux-foundation.org
Subject: [PATCH v15 9/9] Documentation: path-lookup: mention LOOKUP_MAGICLINK_JUMPED
Date: Tue, 5 Nov 2019 20:05:53 +1100 [thread overview]
Message-ID: <20191105090553.6350-10-cyphar@cyphar.com> (raw)
In-Reply-To: <20191105090553.6350-1-cyphar@cyphar.com>
Now that we have a special flag to signify magic-link jumps, mention it
within the path-lookup docs. And now that "magic link" is the correct
term for nd_jump_link()-style symlinks, clean up references to this type
of "symlink".
Signed-off-by: Aleksa Sarai <cyphar@cyphar•com>
---
Documentation/filesystems/path-lookup.rst | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/Documentation/filesystems/path-lookup.rst b/Documentation/filesystems/path-lookup.rst
index 434a07b0002b..2c32795389bd 100644
--- a/Documentation/filesystems/path-lookup.rst
+++ b/Documentation/filesystems/path-lookup.rst
@@ -405,6 +405,10 @@ is requested. Keeping a reference in the ``nameidata`` ensures that
only one root is in effect for the entire path walk, even if it races
with a ``chroot()`` system call.
+It should be noted that in the case of ``LOOKUP_IN_ROOT`` or
+``LOOKUP_BENEATH``, the effective root becomes the directory file descriptor
+passed to ``openat2()`` (which exposes these ``LOOKUP_`` flags).
+
The root is needed when either of two conditions holds: (1) either the
pathname or a symbolic link starts with a "'/'", or (2) a "``..``"
component is being handled, since "``..``" from the root must always stay
@@ -1149,7 +1153,7 @@ so ``NULL`` is returned to indicate that the symlink can be released and
the stack frame discarded.
The other case involves things in ``/proc`` that look like symlinks but
-aren't really::
+aren't really (and are therefore commonly referred to as "magic-links")::
$ ls -l /proc/self/fd/1
lrwx------ 1 neilb neilb 64 Jun 13 10:19 /proc/self/fd/1 -> /dev/pts/4
@@ -1310,12 +1314,14 @@ longer needed.
``LOOKUP_JUMPED`` means that the current dentry was chosen not because
it had the right name but for some other reason. This happens when
following "``..``", following a symlink to ``/``, crossing a mount point
-or accessing a "``/proc/$PID/fd/$FD``" symlink. In this case the
-filesystem has not been asked to revalidate the name (with
-``d_revalidate()``). In such cases the inode may still need to be
-revalidated, so ``d_op->d_weak_revalidate()`` is called if
+or accessing a "``/proc/$PID/fd/$FD``" symlink (also known as a "magic
+link"). In this case the filesystem has not been asked to revalidate the
+name (with ``d_revalidate()``). In such cases the inode may still need
+to be revalidated, so ``d_op->d_weak_revalidate()`` is called if
``LOOKUP_JUMPED`` is set when the look completes - which may be at the
-final component or, when creating, unlinking, or renaming, at the penultimate component.
+final component or, when creating, unlinking, or renaming, at the
+penultimate component. ``LOOKUP_MAGICLINK_JUMPED`` is set alongside
+``LOOKUP_JUMPED`` if a magic-link was traversed.
Final-component flags
~~~~~~~~~~~~~~~~~~~~~
--
2.23.0
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next prev parent reply other threads:[~2019-11-05 9:10 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-05 9:05 [PATCH v15 0/9] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 1/9] namei: LOOKUP_NO_SYMLINKS: block symlink resolution Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 2/9] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution Aleksa Sarai
2019-11-13 1:24 ` Al Viro
2019-11-13 1:24 ` Al Viro
2019-11-05 9:05 ` [PATCH v15 3/9] namei: LOOKUP_NO_XDEV: block mountpoint crossing Aleksa Sarai
2019-11-13 1:36 ` Al Viro
2019-11-13 1:36 ` Al Viro
2019-11-14 4:49 ` Aleksa Sarai
2019-11-14 4:49 ` Aleksa Sarai
2019-11-14 5:43 ` Al Viro
2019-11-14 5:43 ` Al Viro
2019-11-14 13:33 ` Aleksa Sarai
2019-11-14 13:33 ` Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 4/9] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution Aleksa Sarai
2019-11-13 1:55 ` Al Viro
2019-11-13 1:55 ` Al Viro
2019-11-13 7:47 ` Aleksa Sarai
2019-11-13 7:47 ` Aleksa Sarai
2019-11-14 4:57 ` Aleksa Sarai
2019-11-14 4:57 ` Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 5/9] namei: LOOKUP_IN_ROOT: chroot-like " Aleksa Sarai
2019-11-13 2:03 ` Al Viro
2019-11-13 2:03 ` Al Viro
2019-11-13 2:44 ` Aleksa Sarai
2019-11-13 2:44 ` Aleksa Sarai
2019-11-13 2:59 ` Al Viro
2019-11-13 2:59 ` Al Viro
2019-11-13 3:55 ` Aleksa Sarai
2019-11-13 3:55 ` Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 6/9] namei: LOOKUP_{IN_ROOT, BENEATH}: permit limited ".." resolution Aleksa Sarai
2019-11-13 2:09 ` [PATCH v15 6/9] namei: LOOKUP_{IN_ROOT,BENEATH}: " Al Viro
2019-11-13 2:09 ` Al Viro
2019-11-13 7:52 ` Aleksa Sarai
2019-11-13 7:52 ` Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 7/9] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-13 2:29 ` Al Viro
2019-11-13 2:29 ` Al Viro
2019-11-13 2:35 ` Aleksa Sarai
2019-11-13 2:35 ` Aleksa Sarai
2019-11-05 9:05 ` [PATCH v15 8/9] selftests: add openat2(2) selftests Aleksa Sarai
2019-11-05 9:05 ` Aleksa Sarai [this message]
2019-11-11 13:24 ` [PATCH v15 0/9] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-12 23:01 ` Kees Cook
2019-11-12 23:01 ` Kees Cook
2019-11-12 23:06 ` Christian Brauner
2019-11-12 23:06 ` Christian Brauner
2019-11-13 0:46 ` Aleksa Sarai
2019-11-13 0:46 ` Aleksa Sarai
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