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Commit 74dc3384 authored by Aleksa Sarai's avatar Aleksa Sarai Committed by Ingo Molnar
Browse files

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

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: default avatarAleksa Sarai <asarai@suse.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarEric 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: default avatarIngo Molnar <mingo@kernel.org>
parent 18f08dae

fs/proc/base.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

include/linux/sched/debug.h

+3 −1
Original line number Diff line number Diff line
@@ -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

kernel/sched/debug.c

+3 −2
Original line number Diff line number Diff line
@@ -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,

		"---------------------------------------------------------"