diff mbox

[1/7] pipe, sysctl: drop 'min' parameter from pipe-max-size converter

Message ID 20180108053542.6472-2-ebiggers3@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Eric Biggers Jan. 8, 2018, 5:35 a.m. UTC 
From: Eric Biggers <ebiggers@google.com>

Before validating the given value against pipe_min_size,
do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
value up to pipe_min_size.  Therefore, the second check against
pipe_min_size is redundant.  Remove it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/pipe.c                 | 10 +++-------
 include/linux/pipe_fs_i.h |  2 +-
 kernel/sysctl.c           | 15 +--------------
 3 files changed, 5 insertions(+), 22 deletions(-)

Comments

Kees Cook Jan. 9, 2018, 10:20 p.m. UTC | #1 
On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Before validating the given value against pipe_min_size,
> do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
> value up to pipe_min_size.  Therefore, the second check against
> pipe_min_size is redundant.  Remove it.

Well, it's not redundant: it provides a hint to anyone trying to tweak
the sysctl about the minimum value. I think this should stay, but that
pipe_min_size should be made const.

-Kees

>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/pipe.c                 | 10 +++-------
>  include/linux/pipe_fs_i.h |  2 +-
>  kernel/sysctl.c           | 15 +--------------
>  3 files changed, 5 insertions(+), 22 deletions(-)
>
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 6d98566201ef..a75f5d2ca99c 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -35,11 +35,6 @@
>   */
>  unsigned int pipe_max_size = 1048576;
>
> -/*
> - * Minimum pipe size, as required by POSIX
> - */
> -unsigned int pipe_min_size = PAGE_SIZE;
> -
>  /* Maximum allocatable pages per user. Hard limit is unset by default, soft
>   * matches default values.
>   */
> @@ -1024,8 +1019,9 @@ unsigned int round_pipe_size(unsigned int size)
>  {
>         unsigned long nr_pages;
>
> -       if (size < pipe_min_size)
> -               size = pipe_min_size;
> +       /* Minimum pipe size, as required by POSIX */
> +       if (size < PAGE_SIZE)
> +               size = PAGE_SIZE;
>
>         nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>         if (nr_pages == 0)
> diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
> index 2dc5e9870fcd..7d9beda14584 100644
> --- a/include/linux/pipe_fs_i.h
> +++ b/include/linux/pipe_fs_i.h
> @@ -167,7 +167,7 @@ void pipe_lock(struct pipe_inode_info *);
>  void pipe_unlock(struct pipe_inode_info *);
>  void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
>
> -extern unsigned int pipe_max_size, pipe_min_size;
> +extern unsigned int pipe_max_size;
>  extern unsigned long pipe_user_pages_hard;
>  extern unsigned long pipe_user_pages_soft;
>  int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 557d46728577..a71ebb5c5182 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1820,7 +1820,6 @@ static struct ctl_table fs_table[] = {
>                 .maxlen         = sizeof(pipe_max_size),
>                 .mode           = 0644,
>                 .proc_handler   = &pipe_proc_fn,
> -               .extra1         = &pipe_min_size,
>         },
>         {
>                 .procname       = "pipe-user-pages-hard",
> @@ -2622,16 +2621,10 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
>                                  do_proc_douintvec_minmax_conv, &param);
>  }
>
> -struct do_proc_dopipe_max_size_conv_param {
> -       unsigned int *min;
> -};
> -
>  static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
>                                         unsigned int *valp,
>                                         int write, void *data)
>  {
> -       struct do_proc_dopipe_max_size_conv_param *param = data;
> -
>         if (write) {
>                 unsigned int val;
>
> @@ -2642,9 +2635,6 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
>                 if (val == 0)
>                         return -EINVAL;
>
> -               if (param->min && *param->min > val)
> -                       return -ERANGE;
> -
>                 *valp = val;
>         } else {
>                 unsigned int val = *valp;
> @@ -2657,11 +2647,8 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
>  int proc_dopipe_max_size(struct ctl_table *table, int write,
>                          void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
> -       struct do_proc_dopipe_max_size_conv_param param = {
> -               .min = (unsigned int *) table->extra1,
> -       };
>         return do_proc_douintvec(table, write, buffer, lenp, ppos,
> -                                do_proc_dopipe_max_size_conv, &param);
> +                                do_proc_dopipe_max_size_conv, NULL);
>  }
>
>  static void validate_coredump_safety(void)
> --
> 2.15.1
>
Eric Biggers Jan. 10, 2018, 2:29 a.m. UTC | #2 
On Tue, Jan 09, 2018 at 02:20:45PM -0800, Kees Cook wrote:
> On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > Before validating the given value against pipe_min_size,
> > do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
> > value up to pipe_min_size.  Therefore, the second check against
> > pipe_min_size is redundant.  Remove it.
> 
> Well, it's not redundant: it provides a hint to anyone trying to tweak
> the sysctl about the minimum value. I think this should stay, but that
> pipe_min_size should be made const.
> 
> -Kees
> 

It *is* redundant, because it doesn't do anything.  round_pipe_size() already
rounds the value up to the minimum.

Eric
Kees Cook Jan. 10, 2018, 5:30 p.m. UTC | #3 
On Tue, Jan 9, 2018 at 6:29 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> On Tue, Jan 09, 2018 at 02:20:45PM -0800, Kees Cook wrote:
>> On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
>> > From: Eric Biggers <ebiggers@google.com>
>> >
>> > Before validating the given value against pipe_min_size,
>> > do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
>> > value up to pipe_min_size.  Therefore, the second check against
>> > pipe_min_size is redundant.  Remove it.
>>
>> Well, it's not redundant: it provides a hint to anyone trying to tweak
>> the sysctl about the minimum value. I think this should stay, but that
>> pipe_min_size should be made const.
>>
>> -Kees
>>
>
> It *is* redundant, because it doesn't do anything.  round_pipe_size() already
> rounds the value up to the minimum.

Ah, yes, I see it now. Wow are the sysctl functions convoluted here!

Acked-by: Kees Cook <keescook@chromium.org>

-Kees
diff mbox

Patch

diff --git a/fs/pipe.c b/fs/pipe.c
index 6d98566201ef..a75f5d2ca99c 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -35,11 +35,6 @@ 
  */
 unsigned int pipe_max_size = 1048576;
 
-/*
- * Minimum pipe size, as required by POSIX
- */
-unsigned int pipe_min_size = PAGE_SIZE;
-
 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  * matches default values.
  */
@@ -1024,8 +1019,9 @@  unsigned int round_pipe_size(unsigned int size)
 {
 	unsigned long nr_pages;
 
-	if (size < pipe_min_size)
-		size = pipe_min_size;
+	/* Minimum pipe size, as required by POSIX */
+	if (size < PAGE_SIZE)
+		size = PAGE_SIZE;
 
 	nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (nr_pages == 0)
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 2dc5e9870fcd..7d9beda14584 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -167,7 +167,7 @@  void pipe_lock(struct pipe_inode_info *);
 void pipe_unlock(struct pipe_inode_info *);
 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 
-extern unsigned int pipe_max_size, pipe_min_size;
+extern unsigned int pipe_max_size;
 extern unsigned long pipe_user_pages_hard;
 extern unsigned long pipe_user_pages_soft;
 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 557d46728577..a71ebb5c5182 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1820,7 +1820,6 @@  static struct ctl_table fs_table[] = {
 		.maxlen		= sizeof(pipe_max_size),
 		.mode		= 0644,
 		.proc_handler	= &pipe_proc_fn,
-		.extra1		= &pipe_min_size,
 	},
 	{
 		.procname	= "pipe-user-pages-hard",
@@ -2622,16 +2621,10 @@  int proc_douintvec_minmax(struct ctl_table *table, int write,
 				 do_proc_douintvec_minmax_conv, &param);
 }
 
-struct do_proc_dopipe_max_size_conv_param {
-	unsigned int *min;
-};
-
 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
 					unsigned int *valp,
 					int write, void *data)
 {
-	struct do_proc_dopipe_max_size_conv_param *param = data;
-
 	if (write) {
 		unsigned int val;
 
@@ -2642,9 +2635,6 @@  static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
 		if (val == 0)
 			return -EINVAL;
 
-		if (param->min && *param->min > val)
-			return -ERANGE;
-
 		*valp = val;
 	} else {
 		unsigned int val = *valp;
@@ -2657,11 +2647,8 @@  static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
 int proc_dopipe_max_size(struct ctl_table *table, int write,
 			 void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	struct do_proc_dopipe_max_size_conv_param param = {
-		.min = (unsigned int *) table->extra1,
-	};
 	return do_proc_douintvec(table, write, buffer, lenp, ppos,
-				 do_proc_dopipe_max_size_conv, &param);
+				 do_proc_dopipe_max_size_conv, NULL);
 }
 
 static void validate_coredump_safety(void)