Re: [PATCH 13/13] fs: move binfmt_misc sysctl to its own file

[Xiaoming Ni]

On 2020/5/29 15:41, Luis Chamberlain wrote:

This moves the binfmt_misc sysctl to its own file to help remove
clutter from kernel/sysctl.c.

Signed-off-by: Luis Chamberlain 
---
  fs/binfmt_misc.c | 1 +
  kernel/sysctl.c  | 7 ---
  2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index f69a043f562b..656b3f5f3bbf 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -821,6 +821,7 @@ static int __init init_misc_binfmt(void)
int err = register_filesystem(_fs_type);
if (!err)
insert_binfmt(_format);
+   register_sysctl_empty_subdir("fs", "binfmt_misc");
return err;
  }

build error when CONFIG_BINFMT_MISC=m

ERROR: modpost: "register_sysctl_empty_subdir" [fs/binfmt_misc.ko] 
undefined!


diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 27f0c9ea..4129dfb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2853,6 +2853,7 @@ void register_sysctl_empty_subdir(const char *base,
 {
register_sysctl_subdir(base, subdir, sysctl_mount_point);
 }
+EXPORT_SYMBOL_GPL(register_sysctl_empty_subdir);
 #endif /* CONFIG_SYSCTL */


Thanks
Xiaoming Ni

Re: [PATCH 13/13] fs: move binfmt_misc sysctl to its own file

[Kees Cook]

On Fri, May 29, 2020 at 07:41:08AM +, Luis Chamberlain wrote:
> This moves the binfmt_misc sysctl to its own file to help remove
> clutter from kernel/sysctl.c.
> 
> Signed-off-by: Luis Chamberlain 
> ---
>  fs/binfmt_misc.c | 1 +
>  kernel/sysctl.c  | 7 ---
>  2 files changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
> index f69a043f562b..656b3f5f3bbf 100644
> --- a/fs/binfmt_misc.c
> +++ b/fs/binfmt_misc.c
> @@ -821,6 +821,7 @@ static int __init init_misc_binfmt(void)
>   int err = register_filesystem(_fs_type);
>   if (!err)
>   insert_binfmt(_format);
> + register_sysctl_empty_subdir("fs", "binfmt_misc");
>   return err;

Nit: let's make the dir before registering the filesystem. I can't
imagine a realistic situation where userspace is reacting so fast it
would actually fail to mount the fs on /proc/sys/fs/binfmt_misc, but why
risk it?

-Kees

>  }
>  
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 460532cd5ac8..7714e7b476c2 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -3042,13 +3042,6 @@ static struct ctl_table fs_table[] = {
>   .extra1 = SYSCTL_ZERO,
>   .extra2 = SYSCTL_TWO,
>   },
> -#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
> - {
> - .procname   = "binfmt_misc",
> - .mode   = 0555,
> - .child  = sysctl_mount_point,
> - },
> -#endif
>   {
>   .procname   = "pipe-max-size",
>   .data   = _max_size,
> -- 
> 2.26.2
> 

-- 
Kees Cook

[PATCH 13/13] fs: move binfmt_misc sysctl to its own file

[Luis Chamberlain]

This moves the binfmt_misc sysctl to its own file to help remove
clutter from kernel/sysctl.c.

Signed-off-by: Luis Chamberlain 
---
 fs/binfmt_misc.c | 1 +
 kernel/sysctl.c  | 7 ---
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index f69a043f562b..656b3f5f3bbf 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -821,6 +821,7 @@ static int __init init_misc_binfmt(void)
int err = register_filesystem(_fs_type);
if (!err)
insert_binfmt(_format);
+   register_sysctl_empty_subdir("fs", "binfmt_misc");
return err;
 }
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 460532cd5ac8..7714e7b476c2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -3042,13 +3042,6 @@ static struct ctl_table fs_table[] = {
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
},
-#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
-   {
-   .procname   = "binfmt_misc",
-   .mode   = 0555,
-   .child  = sysctl_mount_point,
-   },
-#endif
{
.procname   = "pipe-max-size",
.data   = _max_size,
-- 
2.26.2