Messages in this thread Patch in this message | | | From | Heinrich Schuchardt <> | Subject | [PATCH 3/3] kernel/sysctl.c: threads-max observe limits | Date | Tue, 24 Feb 2015 20:38:21 +0100 |
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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> --- include/linux/sysctl.h | 3 +++ kernel/fork.c | 24 ++++++++++++++++++++++++ kernel/sysctl.c | 6 ++---- 3 files changed, 29 insertions(+), 4 deletions(-)
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 @@ 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 880c78d..52a07c7 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> @@ -2024,3 +2025,26 @@ 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 137c7f6..2e195ae 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -92,11 +92,9 @@ #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; @@ -709,10 +707,10 @@ 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", -- 2.1.4
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