diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index df9b0fe2ed609b35122e716f7bd4693cbebde564..d02b9d0236604e5e1ef2ef5f775f61d7ab5a8d92 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4969,6 +4969,15 @@
switches= [HW,M68k]
+ sysctl.*= [KNL]
+ Set a sysctl parameter, right before loading the init
+ process, as if the value was written to the respective
+ /proc/sys/... file. Both '.' and '/' are recognized as
+ separators. Unrecognized parameters and invalid values
+ are reported in the kernel log. Sysctls registered
+ later by a loaded module cannot be set this way.
+ Example: sysctl.vm.swappiness=40
+
sysfs.deprecated=0|1 [KNL]
Enable/disable old style sysfs layout for old udev
on older distributions. When this option is enabled
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index df2143e05c571e830f71640961a21b1e455fe311..973acf96f37c8a2f390e0f86e07c89a580ec3a1b 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -14,6 +14,7 @@
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bpf-cgroup.h>
+#include <linux/mount.h>
#include "internal.h"
static const struct dentry_operations proc_sys_dentry_operations;
@@ -1703,3 +1704,109 @@ int __init proc_sys_init(void)
return sysctl_init();
}
+
+/* Set sysctl value passed on kernel command line. */
+static int process_sysctl_arg(char *param, char *val,
+ const char *unused, void *arg)
+{
+ char *path;
+ struct vfsmount **proc_mnt = arg;
+ struct file_system_type *proc_fs_type;
+ struct file *file;
+ int len;
+ int err;
+ loff_t pos = 0;
+ ssize_t wret;
+
+ if (strncmp(param, "sysctl", sizeof("sysctl") - 1))
+ return 0;
+
+ param += sizeof("sysctl") - 1;
+
+ if (param[0] != '/' && param[0] != '.')
+ return 0;
+
+ param++;
+
+ /*
+ * To set sysctl options, we use a temporary mount of proc, look up the
+ * respective sys/ file and write to it. To avoid mounting it when no
+ * options were given, we mount it only when the first sysctl option is
+ * found. Why not a persistent mount? There are problems with a
+ * persistent mount of proc in that it forces userspace not to use any
+ * proc mount options.
+ */
+ if (!*proc_mnt) {
+ proc_fs_type = get_fs_type("proc");
+ if (!proc_fs_type) {
+ pr_err("Failed to find procfs to set sysctl from command line\n");
+ return 0;
+ }
+ *proc_mnt = kern_mount(proc_fs_type);
+ put_filesystem(proc_fs_type);
+ if (IS_ERR(*proc_mnt)) {
+ pr_err("Failed to mount procfs to set sysctl from command line\n");
+ return 0;
+ }
+ }
+
+ path = kasprintf(GFP_KERNEL, "sys/%s", param);
+ if (!path)
+ panic("%s: Failed to allocate path for %s\n", __func__, param);
+ strreplace(path, '.', '/');
+
+ file = file_open_root((*proc_mnt)->mnt_root, *proc_mnt, path, O_WRONLY, 0);
+ if (IS_ERR(file)) {
+ err = PTR_ERR(file);
+ if (err == -ENOENT)
+ pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
+ param, val);
+ else if (err == -EACCES)
+ pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
+ param, val);
+ else
+ pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
+ file, param, val);
+ goto out;
+ }
+ len = strlen(val);
+ wret = kernel_write(file, val, len, &pos);
+ if (wret < 0) {
+ err = wret;
+ if (err == -EINVAL)
+ pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
+ param, val);
+ else
+ pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
+ ERR_PTR(err), param, val);
+ } else if (wret != len) {
+ pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
+ wret, len, path, param, val);
+ }
+
+ err = filp_close(file, NULL);
+ if (err)
+ pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
+ ERR_PTR(err), param, val);
+out:
+ kfree(path);
+ return 0;
+}
+
+void do_sysctl_args(void)
+{
+ char *command_line;
+ struct vfsmount *proc_mnt = NULL;
+
+ command_line = kstrdup(saved_command_line, GFP_KERNEL);
+ if (!command_line)
+ panic("%s: Failed to allocate copy of command line\n", __func__);
+
+ parse_args("Setting sysctl args", command_line,
+ NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
+
+ if (proc_mnt)
+ kern_unmount(proc_mnt);
+
+ kfree(command_line);
+}
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index f2401e45a3c2bcc9b409b4474499672fb902e6f8..50bb7f383a1b5dafae9140c90d373ea5d03f8373 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -197,6 +197,7 @@ struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
void unregister_sysctl_table(struct ctl_table_header * table);
extern int sysctl_init(void);
+void do_sysctl_args(void);
extern int pwrsw_enabled;
extern int unaligned_enabled;
@@ -235,6 +236,9 @@ static inline void setup_sysctl_set(struct ctl_table_set *p,
{
}
+static inline void do_sysctl_args(void)
+{
+}
#endif /* CONFIG_SYSCTL */
int sysctl_max_threads(struct ctl_table *table, int write, void *buffer,
diff --git a/init/main.c b/init/main.c
index 76df62fc3e2c55d939039ef42cf453743dbcb91b..b59e093538811eb5488d87f8575e41b0107fe0e0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1412,6 +1412,8 @@ static int __ref kernel_init(void *unused)
rcu_end_inkernel_boot();
+ do_sysctl_args();
+
if (ramdisk_execute_command) {
ret = run_init_process(ramdisk_execute_command);
if (!ret)