[PATCH 1/1] procfs: expose umask in stat and status

From: Pierre Carrier
Date: Fri May 04 2012 - 22:50:35 EST


A new stat field uses decimal, contains umask or -ENOENT if !task->fs.
A new status line is displayed if task->fs, and uses octal.

Signed-off-by: Pierre Carrier <pierre@xxxxxxxxxxx>
---
Tested shortly.

$ awk '{print $NF}' /proc/1/stat
18
$ grep Umask /proc/1/status
Umask: 022
$ umask 077
$ grep Umask /proc/$$/status
Umask: 077
$ umask 0
$ grep Umask /proc/$$/status
Umask: 00

Documentation/filesystems/proc.txt | 2 ++
fs/proc/array.c | 24 +++++++++++++++++++++++-
2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index b7413cb..aa33543 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -212,6 +212,7 @@ Table 1-2: Contents of the status files (as of 2.6.30-rc7)
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
VmPeak peak virtual memory size
@@ -310,6 +311,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
start_data address above which program data+bss is placed
end_data address below which program data+bss is placed
start_brk address above which program heap can be expanded with brk()
+ umask file creation mode mask
..............................................................................

The /proc/PID/maps file containing the currently mapped memory regions and
diff --git a/fs/proc/array.c b/fs/proc/array.c
index f9bd395..5e7d5df 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -81,6 +81,7 @@
#include <linux/pid_namespace.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
+#include <linux/fs_struct.h>

#include <asm/pgtable.h>
#include <asm/processor.h>
@@ -158,11 +159,24 @@ static inline const char *get_task_state(struct task_struct *tsk)
return *p;
}

+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 group_info *group_info;
- int g;
+ int g, umask;
struct fdtable *fdt = NULL;
const struct cred *cred;
pid_t ppid, tpid;
@@ -192,6 +206,10 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
cred->uid, cred->euid, cred->suid, cred->fsuid,
cred->gid, cred->egid, cred->sgid, cred->fsgid);

+ umask = get_task_umask(p);
+ if (umask >= 0)
+ seq_printf(m, "Umask:\t0%o\n", umask);
+
task_lock(p);
if (p->files)
fdt = files_fdtable(p->files);
@@ -368,6 +386,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
pid_t ppid = 0, pgid = -1, sid = -1;
int num_threads = 0;
int permitted;
+ int umask;
struct mm_struct *mm;
unsigned long long start_time;
unsigned long cmin_flt = 0, cmaj_flt = 0;
@@ -462,6 +481,8 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
/* convert nsec -> ticks */
start_time = nsec_to_clock_t(start_time);

+ umask = get_task_umask(task);
+
seq_printf(m, "%d (%s) %c", pid_nr_ns(pid, ns), tcomm, state);
seq_put_decimal_ll(m, ' ', ppid);
seq_put_decimal_ll(m, ' ', pgid);
@@ -511,6 +532,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
seq_put_decimal_ull(m, ' ', (mm && permitted) ? mm->start_data : 0);
seq_put_decimal_ull(m, ' ', (mm && permitted) ? mm->end_data : 0);
seq_put_decimal_ull(m, ' ', (mm && permitted) ? mm->start_brk : 0);
+ seq_put_decimal_ll(m, ' ', umask);
seq_putc(m, '\n');
if (mm)
mmput(mm);
--
1.7.10.1

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