[PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[Petr Vorel]

Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
user_namespace.c.

Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
Hi Christian, all,

I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
solution but IMHO better than use a hardwired number or redefinition in
user_namespace.h.

Kind regards,
Petr

 include/linux/ns_common.h     | 3 +++
 include/linux/pid_namespace.h | 3 ---
 kernel/user_namespace.c       | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index 0f1d024bd958..173fab9dadf7 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -4,6 +4,9 @@
 
 #include <linux/refcount.h>
 
+/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
+#define MAX_PID_NS_LEVEL 32
+
 struct proc_ns_operations;
 
 struct ns_common {
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 07481bb87d4e..f814068012d0 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -11,9 +11,6 @@
 #include <linux/ns_common.h>
 #include <linux/idr.h>
 
-/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
-#define MAX_PID_NS_LEVEL 32
-
 struct fs_pin;
 
 struct pid_namespace {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 5481ba44a8d6..6ea6e263403d 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -87,7 +87,7 @@ int create_user_ns(struct cred *new)
 	int ret, i;
 
 	ret = -ENOSPC;
-	if (parent_ns->level > 32)
+	if (parent_ns->level > MAX_PID_NS_LEVEL)
 		goto fail;
 
 	ucounts = inc_user_namespaces(parent_ns, owner);
-- 
2.35.1

Re: [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[Eric W. Biederman]

Petr Vorel <pvorel@suse.cz> writes:

> Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
> user_namespace.c.

What is the motivation for this change?

Is it just that there is a bare number in create_user_ns and that is a
little ugly?  Or is there something more motivating this?

Eric

>
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
> Hi Christian, all,
>
> I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
> solution but IMHO better than use a hardwired number or redefinition in
> user_namespace.h.
>
> Kind regards,
> Petr
>
>  include/linux/ns_common.h     | 3 +++
>  include/linux/pid_namespace.h | 3 ---
>  kernel/user_namespace.c       | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> index 0f1d024bd958..173fab9dadf7 100644
> --- a/include/linux/ns_common.h
> +++ b/include/linux/ns_common.h
> @@ -4,6 +4,9 @@
>  
>  #include <linux/refcount.h>
>  
> +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> +#define MAX_PID_NS_LEVEL 32
> +
>  struct proc_ns_operations;
>  
>  struct ns_common {
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 07481bb87d4e..f814068012d0 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -11,9 +11,6 @@
>  #include <linux/ns_common.h>
>  #include <linux/idr.h>
>  
> -/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> -#define MAX_PID_NS_LEVEL 32
> -
>  struct fs_pin;
>  
>  struct pid_namespace {
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 5481ba44a8d6..6ea6e263403d 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -87,7 +87,7 @@ int create_user_ns(struct cred *new)
>  	int ret, i;
>  
>  	ret = -ENOSPC;
> -	if (parent_ns->level > 32)
> +	if (parent_ns->level > MAX_PID_NS_LEVEL)
>  		goto fail;
>  
>  	ucounts = inc_user_namespaces(parent_ns, owner);

Re: [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[Christian Brauner]

On Fri, Mar 25, 2022 at 12:21:27PM +0100, Petr Vorel wrote:
> Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
> user_namespace.c.
> 
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
> Hi Christian, all,
> 
> I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
> solution but IMHO better than use a hardwired number or redefinition in
> user_namespace.h.

Hey Petr,

Weird I either deleted that message by accident or didn't get it.

> 
> Kind regards,
> Petr
> 
>  include/linux/ns_common.h     | 3 +++
>  include/linux/pid_namespace.h | 3 ---
>  kernel/user_namespace.c       | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> index 0f1d024bd958..173fab9dadf7 100644
> --- a/include/linux/ns_common.h
> +++ b/include/linux/ns_common.h
> @@ -4,6 +4,9 @@
>  
>  #include <linux/refcount.h>
>  
> +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> +#define MAX_PID_NS_LEVEL 32

The only two namespaces where this applies to have the same hard-coded
limit. If you want to get rid of the raw number you should just
introduce a generic define that expresses the limit for both pidns
and userns. Using "MAX_PID_NS_LEVEL" in the userns case is very
confusing. So if you wanted to do this introducing something like
#define MAX_NS_LEVEL 32
and using it in both places makes more sense.

Christian

Re: [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[Petr Vorel]

> Petr Vorel <pvorel@suse.cz> writes:

> > Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
> > user_namespace.c.

> What is the motivation for this change?

> Is it just that there is a bare number in create_user_ns and that is a
> little ugly?  Or is there something more motivating this?

Well, nothing more than to have constant which gives some description.

Kind regards,
Petr

> Eric


> > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > ---
> > Hi Christian, all,

> > I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
> > solution but IMHO better than use a hardwired number or redefinition in
> > user_namespace.h.

> > Kind regards,
> > Petr

> >  include/linux/ns_common.h     | 3 +++
> >  include/linux/pid_namespace.h | 3 ---
> >  kernel/user_namespace.c       | 2 +-
> >  3 files changed, 4 insertions(+), 4 deletions(-)

> > diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> > index 0f1d024bd958..173fab9dadf7 100644
> > --- a/include/linux/ns_common.h
> > +++ b/include/linux/ns_common.h
> > @@ -4,6 +4,9 @@

> >  #include <linux/refcount.h>

> > +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> > +#define MAX_PID_NS_LEVEL 32
> > +
> >  struct proc_ns_operations;

> >  struct ns_common {
> > diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> > index 07481bb87d4e..f814068012d0 100644
> > --- a/include/linux/pid_namespace.h
> > +++ b/include/linux/pid_namespace.h
> > @@ -11,9 +11,6 @@
> >  #include <linux/ns_common.h>
> >  #include <linux/idr.h>

> > -/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> > -#define MAX_PID_NS_LEVEL 32
> > -
> >  struct fs_pin;

> >  struct pid_namespace {
> > diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> > index 5481ba44a8d6..6ea6e263403d 100644
> > --- a/kernel/user_namespace.c
> > +++ b/kernel/user_namespace.c
> > @@ -87,7 +87,7 @@ int create_user_ns(struct cred *new)
> >  	int ret, i;

> >  	ret = -ENOSPC;
> > -	if (parent_ns->level > 32)
> > +	if (parent_ns->level > MAX_PID_NS_LEVEL)
> >  		goto fail;

> >  	ucounts = inc_user_namespaces(parent_ns, owner);

Re: [PATCH 1/1] ns: Move MAX_PID_NS_LEVEL to ns_common.h, reuse it

[Petr Vorel]

Hi all,

> On Fri, Mar 25, 2022 at 12:21:27PM +0100, Petr Vorel wrote:
> > Move MAX_PID_NS_LEVEL to ns_common.h and reuse it in check in
> > user_namespace.c.

> > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > ---
> > Hi Christian, all,

> > I don't see putting MAX_PID_NS_LEVEL into ns_common.h as an elegant
> > solution but IMHO better than use a hardwired number or redefinition in
> > user_namespace.h.

> Hey Petr,

> Weird I either deleted that message by accident or didn't get it.

Interesting. BTW I didn't get any bounce suggesting mail to you didn't arrive.

> > Kind regards,
> > Petr

> >  include/linux/ns_common.h     | 3 +++
> >  include/linux/pid_namespace.h | 3 ---
> >  kernel/user_namespace.c       | 2 +-
> >  3 files changed, 4 insertions(+), 4 deletions(-)

> > diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> > index 0f1d024bd958..173fab9dadf7 100644
> > --- a/include/linux/ns_common.h
> > +++ b/include/linux/ns_common.h
> > @@ -4,6 +4,9 @@

> >  #include <linux/refcount.h>

> > +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
> > +#define MAX_PID_NS_LEVEL 32

> The only two namespaces where this applies to have the same hard-coded
> limit. If you want to get rid of the raw number you should just
> introduce a generic define that expresses the limit for both pidns
> and userns. Using "MAX_PID_NS_LEVEL" in the userns case is very
> confusing. So if you wanted to do this introducing something like
> #define MAX_NS_LEVEL 32
> and using it in both places makes more sense.

Thanks a lot, I overlooked they aren't related.

I wonder if there should be just one constant for both (i.e. MAX_NS_LEVEL) as
you suggest, 2 constants, i.e keep MAX_PID_NS_LEVEL and add MAX_USER_NS_LEVEL
(which happen to be both 32).

Also understand if you prefer just to keep the raw number (MAX_PID_NS_LEVEL has
more use than just a single place, but user namespaces need it just on single
place).

Kind regards,
Petr

> Christian