Re: [PATCH 3/5] sysctl: remove all extern declaration from sysctl.c

From: Kees Cook
Date: Mon May 04 2020 - 14:43:04 EST

On Fri, Apr 24, 2020 at 08:43:36AM +0200, Christoph Hellwig wrote:
> Extern declarations in .c files are a bad style and can lead to
> mismatches. Use existing definitions in headers where they exist,
> and otherwise move the external declarations to suitable header
> files.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
> include/linux/coredump.h | 4 ++++
> include/linux/file.h | 2 ++
> include/linux/mm.h | 2 ++
> include/linux/mmzone.h | 2 ++
> include/linux/pid.h | 3 +++
> include/linux/sysctl.h | 8 +++++++
> kernel/sysctl.c | 45 +++-------------------------------------
> 7 files changed, 24 insertions(+), 42 deletions(-)
>
> diff --git a/include/linux/coredump.h b/include/linux/coredump.h
> index abf4b4e65dbb9..7a899e83835d5 100644
> --- a/include/linux/coredump.h
> +++ b/include/linux/coredump.h
> @@ -22,4 +22,8 @@ extern void do_coredump(const kernel_siginfo_t *siginfo);
> static inline void do_coredump(const kernel_siginfo_t *siginfo) {}
> #endif
>
> +extern int core_uses_pid;
> +extern char core_pattern[];
> +extern unsigned int core_pipe_limit;
> +
> #endif /* _LINUX_COREDUMP_H */
> diff --git a/include/linux/file.h b/include/linux/file.h
> index 142d102f285e5..122f80084a3ef 100644
> --- a/include/linux/file.h
> +++ b/include/linux/file.h
> @@ -94,4 +94,6 @@ extern void fd_install(unsigned int fd, struct file *file);
> extern void flush_delayed_fput(void);
> extern void __fput_sync(struct file *);
>
> +extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
> +
> #endif /* __LINUX_FILE_H */
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5a323422d783d..9c4e7e76deddc 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3140,5 +3140,7 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping,
> pgoff_t first_index, pgoff_t nr);
> #endif
>
> +extern int sysctl_nr_trim_pages;
> +
> #endif /* __KERNEL__ */
> #endif /* _LINUX_MM_H */
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index f37bb8f187fc7..b2af594ef0f7c 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -909,6 +909,7 @@ static inline int is_highmem(struct zone *zone)
>
> /* These two functions are used to setup the per zone pages min values */
> struct ctl_table;
> +
> int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
> void __user *, size_t *, loff_t *);
> int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,
> @@ -925,6 +926,7 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
>
> extern int numa_zonelist_order_handler(struct ctl_table *, int,
> void __user *, size_t *, loff_t *);
> +extern int percpu_pagelist_fraction;
> extern char numa_zonelist_order[];
> #define NUMA_ZONELIST_ORDER_LEN 16
>
> diff --git a/include/linux/pid.h b/include/linux/pid.h
> index cc896f0fc4e34..93543cbc0e6b3 100644
> --- a/include/linux/pid.h
> +++ b/include/linux/pid.h
> @@ -108,6 +108,9 @@ extern void transfer_pid(struct task_struct *old, struct task_struct *new,
> struct pid_namespace;
> extern struct pid_namespace init_pid_ns;
>
> +extern int pid_max;
> +extern int pid_max_min, pid_max_max;
> +
> /*
> * look up a PID in the hash table. Must be called with the tasklist_lock
> * or rcu_read_lock() held.
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 02fa84493f237..36143ca40b56b 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -207,7 +207,15 @@ void unregister_sysctl_table(struct ctl_table_header * table);
>
> extern int sysctl_init(void);
>
> +extern int pwrsw_enabled;
> +extern int unaligned_enabled;
> +extern int unaligned_dump_stack;
> +extern int no_unaligned_warning;
> +
> extern struct ctl_table sysctl_mount_point[];
> +extern struct ctl_table random_table[];
> +extern struct ctl_table firmware_config_table[];
> +extern struct ctl_table epoll_table[];
>
> #else /* CONFIG_SYSCTL */
> static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 99d27acf46465..31b934865ebc3 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -68,6 +68,9 @@
> #include <linux/bpf.h>
> #include <linux/mount.h>
> #include <linux/userfaultfd_k.h>
> +#include <linux/coredump.h>
> +#include <linux/latencytop.h>
> +#include <linux/pid.h>
>
> #include "../lib/kstrtox.h"
>
> @@ -103,22 +106,6 @@
>
> #if defined(CONFIG_SYSCTL)
>
> -/* External variables not in a header file. */
> -extern int suid_dumpable;
> -#ifdef CONFIG_COREDUMP
> -extern int core_uses_pid;
> -extern char core_pattern[];
> -extern unsigned int core_pipe_limit;
> -#endif
> -extern int pid_max;
> -extern int pid_max_min, pid_max_max;
> -extern int percpu_pagelist_fraction;
> -extern int latencytop_enabled;
> -extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
> -#ifndef CONFIG_MMU
> -extern int sysctl_nr_trim_pages;
> -#endif
> -
> /* Constants used for minimum and maximum */
> #ifdef CONFIG_LOCKUP_DETECTOR
> static int sixty = 60;
> @@ -160,24 +147,6 @@ static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
> #ifdef CONFIG_INOTIFY_USER
> #include <linux/inotify.h>
> #endif
> -#ifdef CONFIG_SPARC
> -#endif
> -
> -#ifdef CONFIG_PARISC
> -extern int pwrsw_enabled;
> -#endif
> -
> -#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW
> -extern int unaligned_enabled;
> -#endif
> -
> -#ifdef CONFIG_IA64
> -extern int unaligned_dump_stack;
> -#endif
> -
> -#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN
> -extern int no_unaligned_warning;
> -#endif
>
> #ifdef CONFIG_PROC_SYSCTL
>
> @@ -243,14 +212,6 @@ static struct ctl_table vm_table[];
> static struct ctl_table fs_table[];
> static struct ctl_table debug_table[];
> static struct ctl_table dev_table[];
> -extern struct ctl_table random_table[];
> -#ifdef CONFIG_EPOLL
> -extern struct ctl_table epoll_table[];
> -#endif
> -
> -#ifdef CONFIG_FW_LOADER_USER_HELPER
> -extern struct ctl_table firmware_config_table[];
> -#endif
>
> #if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
> defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)
> --
> 2.26.1
>

--
Kees Cook