From 16db3d3f1170fb0efca652c9378ce7c5f5cb4232 Mon Sep 17 00:00:00 2001 From: Heinrich Schuchardt Date: Thu, 16 Apr 2015 12:47:50 -0700 Subject: [PATCH] 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 Cc: Oleg Nesterov Cc: Ingo Molnar Cc: Guenter Roeck Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sysctl.h | 3 +++ kernel/fork.c | 31 +++++++++++++++++++++++++++++-- kernel/sysctl.c | 6 ++---- 3 files changed, 34 insertions(+), 6 deletions(-) diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index b7361f831226..795d5fea5697 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -212,4 +212,7 @@ static inline void setup_sysctl_set(struct ctl_table_set *p, #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 c7f2e1a4187a..8807a129711b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -74,6 +74,7 @@ #include #include #include +#include #include #include @@ -266,7 +267,7 @@ void __init __weak arch_task_cache_init(void) { } /* * 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 @@ static void set_max_threads(void) 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 @@ void __init fork_init(void) /* 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 @@ int unshare_files(struct files_struct **displaced) 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 42b7fc2860c1..3c0998426b57 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -93,11 +93,9 @@ #include #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 @@ static struct ctl_table kern_table[] = { #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",