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

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Date:   Mon, 4 May 2020 11:42:58 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Iurii Zaikin <yzaikin@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH 3/5] sysctl: remove all extern declaration from sysctl.c

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@....de>

Reviewed-by: Kees Cook <keescook@...omium.org>

-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