kernel/sysctl.c: threads-max observe limits
Users can change the maximum number of threads by writing to
/proc/sys/kernel/threads-max.
With the patch the value entered is checked against the same limits that
apply when fork_init is called.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index b7361f8..795d5fe 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -212,4 +212,7 @@
#endif /* CONFIG_SYSCTL */
+int sysctl_max_threads(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
#endif /* _LINUX_SYSCTL_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index c7f2e1a..8807a12 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -74,6 +74,7 @@
#include <linux/uprobes.h>
#include <linux/aio.h>
#include <linux/compiler.h>
+#include <linux/sysctl.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -266,7 +267,7 @@
/*
* set_max_threads
*/
-static void set_max_threads(void)
+static void set_max_threads(unsigned int max_threads_suggested)
{
u64 threads;
@@ -280,6 +281,9 @@
threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);
+ if (threads > max_threads_suggested)
+ threads = max_threads_suggested;
+
max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
}
@@ -298,7 +302,7 @@
/* do the arch specific task caches init */
arch_task_cache_init();
- set_max_threads();
+ set_max_threads(MAX_THREADS);
init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
@@ -2020,3 +2024,26 @@
task_unlock(task);
return 0;
}
+
+int sysctl_max_threads(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table t;
+ int ret;
+ int threads = max_threads;
+ int min = MIN_THREADS;
+ int max = MAX_THREADS;
+
+ t = *table;
+ t.data = &threads;
+ t.extra1 = &min;
+ t.extra2 = &max;
+
+ ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+ if (ret || !write)
+ return ret;
+
+ set_max_threads(threads);
+
+ return 0;
+}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 42b7fc2..3c09984 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -93,11 +93,9 @@
#include <linux/nmi.h>
#endif
-
#if defined(CONFIG_SYSCTL)
/* External variables not in a header file. */
-extern int max_threads;
extern int suid_dumpable;
#ifdef CONFIG_COREDUMP
extern int core_uses_pid;
@@ -710,10 +708,10 @@
#endif
{
.procname = "threads-max",
- .data = &max_threads,
+ .data = NULL,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = sysctl_max_threads,
},
{
.procname = "random",