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sched/debug: Use task_pid_nr_ns in /proc/$pid/sched

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It appears as though the addition of the PID namespace did not update
the output code for /proc/*/sched, which resulted in it providing PIDs
that were not self-consistent with the /proc mount. This additionally
made it trivial to detect whether a process was inside &init_pid_ns from
userspace, making container detection trivial:

   https://github.com/jessfraz/amicontained

This leads to situations such as:

  % unshare -pmf
  % mount -t proc proc /proc
  % head -n1 /proc/1/sched
  head (10047, #threads: 1)

Fix this by just using task_pid_nr_ns for the output of /proc/*/sched.
All of the other uses of task_pid_nr in kernel/sched/debug.c are from a
sysctl context and thus don't need to be namespaced.

Signed-off-by: Aleksa Sarai <asarai@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jess Frazelle <acidburn@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: cyphar@cyphar.com
Link: http://lkml.kernel.org/r/20170806044141.5093-1-asarai@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Aleksa Sarai 2017-08-06 14:41:41 +10:00 committed by Ingo Molnar
parent 18f08dae19
commit 74dc3384fc
3 changed files with 8 additions and 4 deletions
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3
fs/proc/base.c
View File

@ -1408,12 +1408,13 @@ static const struct file_operations proc_fail_nth_operations = {
static int sched_show(struct seq_file *m, void *v)
{
struct inode *inode = m->private;
struct pid_namespace *ns = inode->i_sb->s_fs_info;
struct task_struct *p;
p = get_proc_task(inode);
if (!p)
return -ESRCH;
proc_sched_show_task(p, m);
proc_sched_show_task(p, ns, m);
put_task_struct(p);

4
include/linux/sched/debug.h
View File

@ -6,6 +6,7 @@
*/
struct task_struct;
struct pid_namespace;
extern void dump_cpu_task(int cpu);
@ -34,7 +35,8 @@ extern void sched_show_task(struct task_struct *p);
#ifdef CONFIG_SCHED_DEBUG
struct seq_file;
extern void proc_sched_show_task(struct task_struct *p, struct seq_file *m);
extern void proc_sched_show_task(struct task_struct *p,
struct pid_namespace *ns, struct seq_file *m);
extern void proc_sched_set_task(struct task_struct *p);
#endif

5
kernel/sched/debug.c
View File

@ -872,11 +872,12 @@ static void sched_show_numa(struct task_struct *p, struct seq_file *m)
#endif
}
void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
struct seq_file *m)
{
unsigned long nr_switches;
SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid_nr(p),
SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid_nr_ns(p, ns),
get_nr_threads(p));
SEQ_printf(m,
"---------------------------------------------------------"