From: Calvin Owens <calvinowens@fb.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Miklos Szeredi <miklos@szeredi.hu>, Zefan Li <lizefan@huawei.com>,
Oleg Nesterov <oleg@redhat.com>, Joe Perches <joe@perches.com>,
David Howells <dhowells@redhat.com>,
<linux-kernel@vger.kernel.org>, <kernel-team@fb.com>,
<keescook@chromium.org>, Andy Lutomirski <luto@amacapital.net>,
Cyrill Gorcunov <gorcunov@openvz.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [PATCH v7] procfs: Always expose /proc/<pid>/map_files/ and make it readable
Date: Wed, 15 Jul 2015 16:39:22 -0700 [thread overview]
Message-ID: <20150715233922.GA3509821@mail.thefacebook.com> (raw)
In-Reply-To: <20150715152149.0f6158c2c2f806d0be44c110@linux-foundation.org>
On Wednesday 07/15 at 15:21 -0700, Andrew Morton wrote:
> On Thu, 18 Jun 2015 19:32:18 -0700 Calvin Owens <calvinowens@fb.com> wrote:
>
> > Currently, /proc/<pid>/map_files/ is restricted to CAP_SYS_ADMIN, and
> > is only exposed if CONFIG_CHECKPOINT_RESTORE is set.
> >
> > Each mapped file region gets a symlink in /proc/<pid>/map_files/
> > corresponding to the virtual address range at which it is mapped. The
> > symlinks work like the symlinks in /proc/<pid>/fd/, so you can follow
> > them to the backing file even if that backing file has been unlinked.
> >
> > Currently, files which are mapped, unlinked, and closed are impossible
> > to stat() from userspace. Exposing /proc/<pid>/map_files/ closes this
> > functionality "hole".
> >
> > Not being able to stat() such files makes noticing and explicitly
> > accounting for the space they use on the filesystem impossible. You can
> > work around this by summing up the space used by every file in the
> > filesystem and subtracting that total from what statfs() tells you, but
> > that obviously isn't great, and it becomes unworkable once your
> > filesystem becomes large enough.
> >
> > This patch moves map_files/ out from behind CONFIG_CHECKPOINT_RESTORE,
> > and adjusts the permissions enforced on it as follows:
>
> proc_pid_follow_link() got changed while you weren't looking, causing
>
> fs/proc/base.c: In function 'proc_map_files_follow_link':
> fs/proc/base.c:1963: warning: passing argument 2 of 'proc_pid_follow_link' from incompatible pointer type
> fs/proc/base.c:1578: note: expected 'void **' but argument is of type 'struct nameidata *'
> fs/proc/base.c:1963: warning: return discards qualifiers from pointer target type
> fs/proc/base.c: At top level:
> fs/proc/base.c:1971: warning: initialization from incompatible pointer type
>
> I just changed it to pass NULL:
Thanks for cleaning this up, I'll make sure to check outstanding patches
against new -rcs and -nexts in the future.
Thanks,
Calvin
> --- a/fs/proc/base.c~procfs-always-expose-proc-pid-map_files-and-make-it-readable-fix
> +++ a/fs/proc/base.c
> @@ -1955,12 +1955,13 @@ struct map_files_info {
> * symlinks may be used to bypass permissions on ancestor directories in the
> * path to the file in question.
> */
> -static void *proc_map_files_follow_link(struct dentry *dentry, struct nameidata *nd)
> +static void *
> +proc_map_files_follow_link(struct dentry *dentry, struct nameidata *nd)
> {
> if (!capable(CAP_SYS_ADMIN))
> return ERR_PTR(-EPERM);
>
> - return proc_pid_follow_link(dentry, nd);
> + return proc_pid_follow_link(dentry, NULL);
> }
>
> /*
> _
>
next prev parent reply other threads:[~2015-07-15 23:40 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-14 0:20 [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Calvin Owens
2015-01-14 0:23 ` Calvin Owens
2015-01-14 14:13 ` Rasmus Villemoes
2015-01-14 14:37 ` Siddhesh Poyarekar
2015-01-14 14:53 ` Rasmus Villemoes
2015-01-14 21:03 ` Calvin Owens
2015-01-14 22:45 ` Andrew Morton
2015-01-14 23:51 ` Rasmus Villemoes
2015-01-16 1:15 ` Andrew Morton
2015-01-16 11:00 ` Kirill A. Shutemov
2015-01-14 15:25 ` Kirill A. Shutemov
2015-01-14 15:33 ` Cyrill Gorcunov
2015-01-14 20:46 ` Calvin Owens
2015-01-14 21:16 ` Cyrill Gorcunov
2015-01-22 2:45 ` [RFC][PATCH] procfs: Always expose /proc/<pid>/map_files/ and make it readable Calvin Owens
2015-01-22 7:16 ` Cyrill Gorcunov
2015-01-22 11:02 ` Kirill A. Shutemov
2015-01-22 21:00 ` Calvin Owens
2015-01-22 21:27 ` Kirill A. Shutemov
2015-01-23 5:52 ` Calvin Owens
2015-01-24 3:15 ` [RFC][PATCH v2] " Calvin Owens
2015-01-26 12:47 ` Kirill A. Shutemov
2015-01-26 21:00 ` Cyrill Gorcunov
2015-01-26 23:43 ` Andrew Morton
2015-01-27 0:15 ` Kees Cook
2015-01-27 7:37 ` Cyrill Gorcunov
2015-01-27 19:53 ` Kees Cook
2015-01-27 21:35 ` Cyrill Gorcunov
2015-01-27 21:46 ` Pavel Emelyanov
2015-01-27 0:19 ` Kirill A. Shutemov
2015-01-27 6:46 ` Cyrill Gorcunov
2015-01-27 6:50 ` Andrew Morton
2015-01-27 7:23 ` Cyrill Gorcunov
2015-01-28 4:38 ` Calvin Owens
2015-01-30 1:30 ` Kees Cook
2015-01-31 1:58 ` Calvin Owens
2015-02-02 14:01 ` Austin S Hemmelgarn
2015-02-04 3:53 ` Calvin Owens
2015-02-02 20:16 ` Andy Lutomirski
2015-02-04 3:28 ` Calvin Owens
2015-02-12 2:29 ` [RFC][PATCH v3] " Calvin Owens
2015-02-12 7:45 ` Cyrill Gorcunov
2015-02-14 20:40 ` [RFC][PATCH v4] " Calvin Owens
2015-03-10 22:17 ` Cyrill Gorcunov
2015-04-28 22:23 ` Calvin Owens
2015-04-29 7:32 ` Cyrill Gorcunov
2015-05-19 3:10 ` [PATCH v5] " Calvin Owens
2015-05-19 3:29 ` Joe Perches
2015-05-19 18:04 ` Andy Lutomirski
2015-05-21 1:52 ` Calvin Owens
2015-05-21 2:10 ` Andy Lutomirski
2015-06-09 3:39 ` [PATCH v6] " Calvin Owens
2015-06-09 17:27 ` Kees Cook
2015-06-09 17:47 ` Andy Lutomirski
2015-06-09 18:15 ` Cyrill Gorcunov
2015-06-09 21:13 ` Andrew Morton
2015-06-10 1:39 ` Calvin Owens
2015-06-10 20:58 ` Andrew Morton
2015-06-11 11:10 ` Alexey Dobriyan
2015-06-11 18:49 ` Andrew Morton
2015-06-12 9:55 ` Alexey Dobriyan
2015-06-19 2:32 ` [PATCH v7] " Calvin Owens
2015-07-15 22:21 ` Andrew Morton
2015-07-15 23:39 ` Calvin Owens [this message]
2015-02-14 20:44 ` [PATCH] procfs: Return -ESRCH on /proc/N/fd/* when PID N doesn't exist Calvin Owens
2015-01-14 22:40 ` [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Kirill A. Shutemov
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