linux-kernel - Re: [PATCH] procfs: expose umask in /proc/<PID>/status

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <570F6F37.50209@redhat.com>
Date:	Thu, 14 Apr 2016 12:21:43 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	"Richard W.M. Jones" <rjones@...hat.com>, corbet@....net
Cc:	akpm@...ux-foundation.org, vbabka@...e.cz, mhocko@...e.com,
	hughd@...gle.com, koct9i@...il.com, chenhanxiao@...fujitsu.com,
	n-horiguchi@...jp.nec.com, ross.zwisler@...ux.intel.com,
	john.stultz@...aro.org, minchan@...nel.org, hannes@...xchg.org,
	nathans@...hat.com, andriy.shevchenko@...ux.intel.com,
	keescook@...omium.org, gorcunov@...nvz.org, joe@...ches.com,
	linux@...musvillemoes.dk, mingo@...nel.org, cmetcalf@...hip.com,
	iago@...ocode.com, luto@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, gorcunov@...il.com, fw@...eb.enyo.de,
	walters@...bum.org
Subject: Re: [PATCH] procfs: expose umask in /proc/<PID>/status

On 04/14/2016 11:34 AM, Richard W.M. Jones wrote:
> It's not possible to read the process umask without also modifying it,
> which is what umask(2) does.  A library cannot read umask safely,
> especially if the main program might be multithreaded.
> 
> Add a new status line ("Umask") in /proc/<PID>/status.  It contains
> the file mode creation mask (umask) in octal.  It is only shown for
> tasks which have task->fs.
> 
> This patch is adapted from one originally written by Pierre Carrier.
> 
> Signed-off-by: Richard W.M. Jones <rjones@...hat.com>
> ---
>  Documentation/filesystems/proc.txt |  1 +
>  fs/proc/array.c                    | 20 +++++++++++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
> index 7f5607a..e8d0075 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -225,6 +225,7 @@ Table 1-2: Contents of the status files (as of 4.1)
>   TracerPid                   PID of process tracing this process (0 if not)
>   Uid                         Real, effective, saved set, and  file system UIDs
>   Gid                         Real, effective, saved set, and  file system GIDs
> + Umask                       file mode creation mask
>   FDSize                      number of file descriptor slots currently allocated
>   Groups                      supplementary group list
>   NStgid                      descendant namespace thread group ID hierarchy
> diff --git a/fs/proc/array.c b/fs/proc/array.c
> index b6c00ce..03e8d3f 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -83,6 +83,7 @@
>  #include <linux/tracehook.h>
>  #include <linux/string_helpers.h>
>  #include <linux/user_namespace.h>
> +#include <linux/fs_struct.h>
>  
>  #include <asm/pgtable.h>
>  #include <asm/processor.h>
> @@ -139,12 +140,25 @@ static inline const char *get_task_state(struct task_struct *tsk)
>  	return task_state_array[fls(state)];
>  }
>  
> +static inline int get_task_umask(struct task_struct *tsk)
> +{
> +	struct fs_struct *fs;
> +	int umask = -ENOENT;
> +
> +	task_lock(tsk);
> +	fs = tsk->fs;
> +	if (fs)
> +		umask = fs->umask;
> +	task_unlock(tsk);
> +	return umask;
> +}
> +
>  static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
>  				struct pid *pid, struct task_struct *p)
>  {
>  	struct user_namespace *user_ns = seq_user_ns(m);
>  	struct group_info *group_info;
> -	int g;
> +	int g, umask;
>  	struct task_struct *tracer;
>  	const struct cred *cred;
>  	pid_t ppid, tpid = 0, tgid, ngid;
> @@ -162,6 +176,10 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
>  	ngid = task_numa_group_id(p);
>  	cred = get_task_cred(p);
>  
> +	umask = get_task_umask(p);
> +	if (umask >= 0)
> +		seq_printf(m, "Umask:\t0%o\n", umask);

It seems to me that umasks are usually displayed in the form 0XXX, such
as the output of umask command. So what about:

seq_printf(m, "Umask:\t%#04o\n", umask);

Provided printk() supports those flags, of course.

Thanks,
Jerome

> +
>  	task_lock(p);
>  	if (p->files)
>  		max_fds = files_fdtable(p->files)->max_fds;
> 




Download attachment "signature.asc" of type "application/pgp-signature" (474 bytes)