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Subject[PATCH] protect migration/%d etc from sched_setaffinity
Lock out users from changing the cpu affinity of those per-cpu system
daemons which cannot survive such a change, such as migration/%d.

Passes basic handtest of sched_setaffinity(2) on various locked and
unlocked processes on a i386, otherwise untested except by eyeball.

Except for one line in i386, no arch needed any changes to support
this patch.

Joe


arch/i386/kernel/apm.c | 1 +
include/linux/sched.h | 1 +
kernel/fork.c | 2 +-
kernel/module.c | 2 ++
kernel/sched.c | 4 ++++
kernel/softirq.c | 4 ++--
kernel/workqueue.c | 1 +
mm/vmscan.c | 5 ++++-
8 files changed, 16 insertions(+), 4 deletions(-)


diff -Nura linux-2.6.0-test2/arch/i386/kernel/apm.c.orig linux-2.6.0-test2/arch/i386/kernel/apm.c
--- linux-2.6.0-test2/arch/i386/kernel/apm.c.orig 2003-07-31 10:36:23.000000000 -0400
+++ linux-2.6.0-test2/arch/i386/kernel/apm.c 2003-07-31 15:52:25.000000000 -0400
@@ -1705,6 +1705,7 @@
* Method suggested by Ingo Molnar.
*/
set_cpus_allowed(current, 1UL << 0);
+ current->flags |= PF_CPULOCK;
BUG_ON(smp_processor_id() != 0);
#endif

diff -Nura linux-2.6.0-test2/include/linux/sched.h.orig linux-2.6.0-test2/include/linux/sched.h
--- linux-2.6.0-test2/include/linux/sched.h.orig 2003-07-27 12:57:39.000000000 -0400
+++ linux-2.6.0-test2/include/linux/sched.h 2003-07-31 15:52:25.000000000 -0400
@@ -488,6 +488,7 @@
#define PF_LESS_THROTTLE 0x01000000 /* Throttle me less: I clena memory */
#define PF_SYNCWRITE 0x00200000 /* I am doing a sync write */
#define PF_READAHEAD 0x00400000 /* I am doing read-ahead */
+#define PF_CPULOCK 0x00800000 /* lock users out from changing cpus_allowed */

#ifdef CONFIG_SMP
extern int set_cpus_allowed(task_t *p, unsigned long new_mask);
diff -Nura linux-2.6.0-test2/kernel/sched.c.orig linux-2.6.0-test2/kernel/sched.c
--- linux-2.6.0-test2/kernel/sched.c.orig 2003-07-27 13:07:14.000000000 -0400
+++ linux-2.6.0-test2/kernel/sched.c 2003-07-31 18:16:20.000000000 -0400
@@ -1930,6 +1930,9 @@
if ((current->euid != p->euid) && (current->euid != p->uid) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
+ if (p->flags & PF_CPULOCK) {
+ goto out_unlock;
+ }

retval = set_cpus_allowed(p, new_mask);

@@ -2380,6 +2383,7 @@
* serially).
*/
set_cpus_allowed(current, 1UL << cpu);
+ current->flags |= PF_CPULOCK;

ret = setscheduler(0, SCHED_FIFO, &param);

diff -Nura linux-2.6.0-test2/kernel/softirq.c.orig linux-2.6.0-test2/kernel/softirq.c
--- linux-2.6.0-test2/kernel/softirq.c.orig 2003-07-27 12:58:53.000000000 -0400
+++ linux-2.6.0-test2/kernel/softirq.c 2003-07-31 15:52:25.000000000 -0400
@@ -323,8 +323,8 @@

/* Migrate to the right CPU */
set_cpus_allowed(current, 1UL << cpu);
- if (smp_processor_id() != cpu)
- BUG();
+ current->flags |= PF_CPULOCK;
+ BUG_ON(smp_processor_id() != cpu);

__set_current_state(TASK_INTERRUPTIBLE);
mb();
diff -Nura linux-2.6.0-test2/kernel/module.c.orig linux-2.6.0-test2/kernel/module.c
--- linux-2.6.0-test2/kernel/module.c.orig 2003-07-27 13:06:11.000000000 -0400
+++ linux-2.6.0-test2/kernel/module.c 2003-07-31 15:52:25.000000000 -0400
@@ -483,6 +483,7 @@
setscheduler(current->pid, SCHED_FIFO, &param);
#endif
set_cpus_allowed(current, 1UL << (unsigned long)cpu);
+ current->flags |= PF_CPULOCK;

/* Ack: we are alive */
atomic_inc(&stopref_thread_ack);
@@ -544,6 +545,7 @@
/* FIXME: racy with set_cpus_allowed. */
old_allowed = current->cpus_allowed;
set_cpus_allowed(current, 1UL << (unsigned long)cpu);
+ current->flags |= PF_CPULOCK;

atomic_set(&stopref_thread_ack, 0);
stopref_num_threads = 0;
diff -Nura linux-2.6.0-test2/kernel/fork.c.orig linux-2.6.0-test2/kernel/fork.c
--- linux-2.6.0-test2/kernel/fork.c.orig 2003-07-27 12:57:39.000000000 -0400
+++ linux-2.6.0-test2/kernel/fork.c 2003-07-31 15:52:25.000000000 -0400
@@ -705,7 +705,7 @@
{
unsigned long new_flags = p->flags;

- new_flags &= ~PF_SUPERPRIV;
+ new_flags &= ~(PF_SUPERPRIV | PF_CPULOCK);
new_flags |= PF_FORKNOEXEC;
if (!(clone_flags & CLONE_PTRACE))
p->ptrace = 0;
diff -Nura linux-2.6.0-test2/kernel/workqueue.c.orig linux-2.6.0-test2/kernel/workqueue.c
--- linux-2.6.0-test2/kernel/workqueue.c.orig 2003-07-27 13:11:08.000000000 -0400
+++ linux-2.6.0-test2/kernel/workqueue.c 2003-07-31 15:52:25.000000000 -0400
@@ -177,6 +177,7 @@

set_user_nice(current, -10);
set_cpus_allowed(current, 1UL << cpu);
+ current->flags |= PF_CPULOCK;

complete(&startup->done);

diff -Nura linux-2.6.0-test2/mm/vmscan.c.orig linux-2.6.0-test2/mm/vmscan.c
--- linux-2.6.0-test2/mm/vmscan.c.orig 2003-07-27 12:57:44.000000000 -0400
+++ linux-2.6.0-test2/mm/vmscan.c 2003-07-31 15:52:25.000000000 -0400
@@ -960,8 +960,11 @@

daemonize("kswapd%d", pgdat->node_id);
cpumask = node_to_cpumask(pgdat->node_id);
- if (cpumask)
+ if (cpumask) {
set_cpus_allowed(tsk, cpumask);
+ /* FIXME: a node version of PF_CPULOCK would be cool */
+ current->flags |= PF_CPULOCK;
+ }
current->reclaim_state = &reclaim_state;

/*
-
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