* [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) @ 2016-04-14 9:34 Richard W.M. Jones 2016-04-14 9:34 ` [PATCH] procfs: expose umask in /proc/<PID>/status Richard W.M. Jones 2016-04-14 9:36 ` [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) Richard W.M. Jones 0 siblings, 2 replies; 4+ messages in thread From: Richard W.M. Jones @ 2016-04-14 9:34 UTC (permalink / raw) To: corbet Cc: akpm, vbabka, mhocko, hughd, koct9i, chenhanxiao, n-horiguchi, ross.zwisler, john.stultz, minchan, jmarchan, hannes, nathans, andriy.shevchenko, keescook, gorcunov, joe, linux, mingo, cmetcalf, iago, luto, linux-doc, linux-kernel, gorcunov, fw, walters 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. For the library this allows me to read the umask from /proc/self/status. This patch is adapted from one originally written by Pierre Carrier: https://lkml.org/lkml/2012/5/4/451 Rich. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] procfs: expose umask in /proc/<PID>/status 2016-04-14 9:34 [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) Richard W.M. Jones @ 2016-04-14 9:34 ` Richard W.M. Jones 2016-04-14 10:21 ` Jerome Marchand 2016-04-14 9:36 ` [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) Richard W.M. Jones 1 sibling, 1 reply; 4+ messages in thread From: Richard W.M. Jones @ 2016-04-14 9:34 UTC (permalink / raw) To: corbet Cc: akpm, vbabka, mhocko, hughd, koct9i, chenhanxiao, n-horiguchi, ross.zwisler, john.stultz, minchan, jmarchan, hannes, nathans, andriy.shevchenko, keescook, gorcunov, joe, linux, mingo, cmetcalf, iago, luto, linux-doc, linux-kernel, gorcunov, fw, walters 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@redhat.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); + task_lock(p); if (p->files) max_fds = files_fdtable(p->files)->max_fds; -- 2.7.4 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] procfs: expose umask in /proc/<PID>/status 2016-04-14 9:34 ` [PATCH] procfs: expose umask in /proc/<PID>/status Richard W.M. Jones @ 2016-04-14 10:21 ` Jerome Marchand 0 siblings, 0 replies; 4+ messages in thread From: Jerome Marchand @ 2016-04-14 10:21 UTC (permalink / raw) To: Richard W.M. Jones, corbet Cc: akpm, vbabka, mhocko, hughd, koct9i, chenhanxiao, n-horiguchi, ross.zwisler, john.stultz, minchan, hannes, nathans, andriy.shevchenko, keescook, gorcunov, joe, linux, mingo, cmetcalf, iago, luto, linux-doc, linux-kernel, gorcunov, fw, walters [-- Attachment #1.1: Type: text/plain, Size: 3280 bytes --] 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@redhat.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; > [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 473 bytes --] ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) 2016-04-14 9:34 [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask) Richard W.M. Jones 2016-04-14 9:34 ` [PATCH] procfs: expose umask in /proc/<PID>/status Richard W.M. Jones @ 2016-04-14 9:36 ` Richard W.M. Jones 1 sibling, 0 replies; 4+ messages in thread From: Richard W.M. Jones @ 2016-04-14 9:36 UTC (permalink / raw) To: corbet Cc: akpm, vbabka, mhocko, hughd, koct9i, chenhanxiao, n-horiguchi, ross.zwisler, john.stultz, minchan, jmarchan, hannes, nathans, andriy.shevchenko, keescook, gorcunov, joe, linux, mingo, cmetcalf, iago, luto, linux-doc, linux-kernel, gorcunov, fw, walters On Thu, Apr 14, 2016 at 10:34:48AM +0100, 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. > > For the library this allows me to read the umask from > /proc/self/status. > > This patch is adapted from one originally written by Pierre Carrier: > https://lkml.org/lkml/2012/5/4/451 Sorry, I meant to add an example of what this looks like: $ grep Umask /proc/1/status Umask: 022 $ grep Umask /proc/2/status Umask: 022 $ grep Umask /proc/self/status Umask: 022 $ umask 002 $ grep Umask /proc/self/status Umask: 02 Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top ^ permalink raw reply [flat|nested] 4+ messages in thread
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