Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Aleksa Sarai <cyphar@cyphar.com>, Al Viro <viro@zeniv.linux.org.uk>
Cc: mtk.manpages@gmail.com, Christian Brauner <christian@brauner.io>,
	Aleksa Sarai <asarai@suse.de>,
	linux-man@vger.kernel.org, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH man-pages v2 1/2] path_resolution.7: update to mention openat2(2) features
Date: Mon, 30 Mar 2020 22:38:51 +0200	[thread overview]
Message-ID: <0b3289e5-06b9-63a3-8a19-56e2551d2ce0@gmail.com> (raw)
In-Reply-To: <20200202151907.23587-2-cyphar@cyphar.com>

Hello Aleksa,

On 2/2/20 4:19 PM, Aleksa Sarai wrote:
> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

Thanks. I've applied this patch.

Cheers,

Michael

> ---
>  man7/path_resolution.7 | 56 ++++++++++++++++++++++++++++--------------
>  1 file changed, 38 insertions(+), 18 deletions(-)
> 
> diff --git a/man7/path_resolution.7 b/man7/path_resolution.7
> index 07664ed8faec..b4a65cc53120 100644
> --- a/man7/path_resolution.7
> +++ b/man7/path_resolution.7
> @@ -29,30 +29,38 @@ path_resolution \- how a pathname is resolved to a file
>  Some UNIX/Linux system calls have as parameter one or more filenames.
>  A filename (or pathname) is resolved as follows.
>  .SS Step 1: start of the resolution process
> -If the pathname starts with the \(aq/\(aq character,
> -the starting lookup directory
> -is the root directory of the calling process.
> -(A process inherits its
> -root directory from its parent.
> -Usually this will be the root directory
> -of the file hierarchy.
> -A process may get a different root directory
> -by use of the
> +If the pathname starts with the \(aq/\(aq character, the starting lookup
> +directory is the root directory of the calling process.
> +A process inherits its root directory from its parent.
> +Usually this will be the root directory of the file hierarchy.
> +A process may get a different root directory by use of the
>  .BR chroot (2)
> -system call.
> +system call, or may temporarily use a different root directory by using
> +.BR openat2 (2)
> +with the
> +.B RESOLVE_IN_ROOT
> +flag set.
> +.PP
>  A process may get an entirely private mount namespace in case
>  it\(emor one of its ancestors\(emwas started by an invocation of the
>  .BR clone (2)
>  system call that had the
>  .B CLONE_NEWNS
> -flag set.)
> +flag set.
>  This handles the \(aq/\(aq part of the pathname.
>  .PP
> -If the pathname does not start with the \(aq/\(aq character, the
> -starting lookup directory of the resolution process is the current working
> -directory of the process.
> -(This is also inherited from the parent.
> -It can be changed by use of the
> +If the pathname does not start with the \(aq/\(aq character, the starting
> +lookup directory of the resolution process is the current working directory of
> +the process \(em or in the case of
> +.BR openat (2)-style
> +system calls, the
> +.I dfd
> +argument (or the current working directory if
> +.B AT_FDCWD
> +is passed as the
> +.I dfd
> +argument). The current working directory is inherited from the parent, and can
> +be changed by use of the
>  .BR chdir (2)
>  system call.)
>  .PP
> @@ -91,7 +99,7 @@ Upon error, that error is returned.
>  If the result is not a directory, an
>  .B ENOTDIR
>  error is returned.
> -If the resolution of the symlink is successful and returns a directory,
> +If the resolution of the symbolic link is successful and returns a directory,
>  we set the current lookup directory to that directory, and go to
>  the next component.
>  Note that the resolution process here can involve recursion if the
> @@ -124,6 +132,12 @@ the kernel's pathname-resolution code
>  was reworked to eliminate the use of recursion,
>  so that the only limit that remains is the maximum of 40
>  resolutions for the entire pathname.
> +.PP
> +The resolution of symbolic links during this stage can be blocked by using
> +.BR openat2 (2),
> +with the
> +.B RESOLVE_NO_SYMLINKS
> +flag set.
>  .SS Step 3: find the final entry
>  The lookup of the final component of the pathname goes just like
>  that of all other components, as described in the previous step,
> @@ -145,7 +159,7 @@ The path resolution process will assume that these entries have
>  their conventional meanings, regardless of whether they are
>  actually present in the physical filesystem.
>  .PP
> -One cannot walk down past the root: "/.." is the same as "/".
> +One cannot walk up past the root: "/.." is the same as "/".
>  .SS Mount points
>  After a "mount dev path" command, the pathname "path" refers to
>  the root of the filesystem hierarchy on the device "dev", and no
> @@ -154,6 +168,12 @@ longer to whatever it referred to earlier.
>  One can walk out of a mounted filesystem: "path/.." refers to
>  the parent directory of "path",
>  outside of the filesystem hierarchy on "dev".
> +.PP
> +Traversal of mount points can be blocked by using
> +.BR openat2 (2),
> +with the
> +.B RESOLVE_NO_XDEV
> +flag set (though note that this also restricts bind mount traversal).
>  .SS Trailing slashes
>  If a pathname ends in a \(aq/\(aq, that forces resolution of the preceding
>  component as in Step 2: it has to exist and resolve to a directory.
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

  reply	other threads:[~2020-03-30 20:39 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-02 15:19 [PATCH man-pages v2 0/2] document openat2(2) Aleksa Sarai
2020-02-02 15:19 ` [PATCH man-pages v2 1/2] path_resolution.7: update to mention openat2(2) features Aleksa Sarai
2020-03-30 20:38   ` Michael Kerrisk (man-pages) [this message]
2020-02-02 15:19 ` [PATCH man-pages v2 2/2] openat2.2: document new openat2(2) syscall Aleksa Sarai
2020-03-30  9:08   ` Michael Kerrisk (man-pages)
2020-03-30  9:20     ` Aleksa Sarai
2020-03-30  9:36       ` Michael Kerrisk (man-pages)
2020-03-30  9:48         ` Aleksa Sarai
2020-03-30 20:43   ` Michael Kerrisk (man-pages)
2020-03-31 14:39     ` Aleksa Sarai
2020-04-01  6:38       ` Michael Kerrisk (man-pages)
2020-04-08 21:29         ` Michael Kerrisk (man-pages)
2020-04-12 16:49         ` Aleksa Sarai
2020-04-13  7:22           ` Michael Kerrisk (man-pages)
2020-04-14 10:35             ` Aleksa Sarai
2020-04-15 20:24               ` Michael Kerrisk (man-pages)
2020-05-04 10:17               ` Michael Kerrisk (man-pages)
2020-06-10  5:53               ` [PATCH] symlink.7: document magic-links more completely Aleksa Sarai
2020-06-19 13:00                 ` Michael Kerrisk (man-pages)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=0b3289e5-06b9-63a3-8a19-56e2551d2ce0@gmail.com \
    --to=mtk.manpages@gmail.com \
    --cc=asarai@suse.de \
    --cc=christian@brauner.io \
    --cc=cyphar@cyphar.com \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-man@vger.kernel.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH man-pages v2 1/2] path_resolution.7: update to mention openat2(2) features' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).