[PATCH] Remove READ_IMPLIES_EXEC during restart

[PATCH] Remove READ_IMPLIES_EXEC during restart

[Dan Smith]

On s390, all tasks have READ_IMPLIES_EXEC set in current->personality,
which causes the restart process to map things like the stack and heap as
executable.  During the restart process, remove this bit and restore the
original personality afterwards.

This seems a little ugly, but I don't know that there's a better place for
it.

Cc: orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org
Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 checkpoint/restart.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index adebc1c..8958ec7 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -13,6 +13,7 @@
 #include <linux/wait.h>
 #include <linux/file.h>
 #include <linux/magic.h>
+#include <linux/personality.h>
 #include <linux/checkpoint.h>
 #include <linux/checkpoint_hdr.h>
 
@@ -535,12 +536,18 @@ static int do_restart_root(struct cr_ctx *ctx, pid_t pid)
 int do_restart(struct cr_ctx *ctx, pid_t pid)
 {
 	int ret;
+	unsigned int original_personality;
+	
+	original_personality = current->personality;
+	current->personality &= ~READ_IMPLIES_EXEC;
 
 	if (ctx)
 		ret = do_restart_root(ctx, pid);
 	else
 		ret = do_restart_task(pid);
 
+	current->personality = original_personality;
+
 	/* on success, adjust the return value if needed [TODO] */
 	return ret;
 }
-- 
1.6.1

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Serge E. Hallyn]

Quoting Dan Smith (danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org):
> On s390, all tasks have READ_IMPLIES_EXEC set in current->personality,
> which causes the restart process to map things like the stack and heap as
> executable.  During the restart process, remove this bit and restore the
> original personality afterwards.
> 
> This seems a little ugly, but I don't know that there's a better place for
> it.

Well imo the only other thing to do would be to do the same thing but
just around the main restart_memory function.

> Cc: orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org
> Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

> ---
>  checkpoint/restart.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
> index adebc1c..8958ec7 100644
> --- a/checkpoint/restart.c
> +++ b/checkpoint/restart.c
> @@ -13,6 +13,7 @@
>  #include <linux/wait.h>
>  #include <linux/file.h>
>  #include <linux/magic.h>
> +#include <linux/personality.h>
>  #include <linux/checkpoint.h>
>  #include <linux/checkpoint_hdr.h>
> 
> @@ -535,12 +536,18 @@ static int do_restart_root(struct cr_ctx *ctx, pid_t pid)
>  int do_restart(struct cr_ctx *ctx, pid_t pid)
>  {
>  	int ret;
> +	unsigned int original_personality;
> +	
> +	original_personality = current->personality;
> +	current->personality &= ~READ_IMPLIES_EXEC;
> 
>  	if (ctx)
>  		ret = do_restart_root(ctx, pid);
>  	else
>  		ret = do_restart_task(pid);
> 
> +	current->personality = original_personality;
> +
>  	/* on success, adjust the return value if needed [TODO] */
>  	return ret;
>  }
> -- 
> 1.6.1
> 
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Oren Laadan]

Serge E. Hallyn wrote:
> Quoting Dan Smith (danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org):
>> On s390, all tasks have READ_IMPLIES_EXEC set in current->personality,
>> which causes the restart process to map things like the stack and heap as
>> executable.  During the restart process, remove this bit and restore the
>> original personality afterwards.
>>
>> This seems a little ugly, but I don't know that there's a better place for
>> it.
> 
> Well imo the only other thing to do would be to do the same thing but
> just around the main restart_memory function.
> 

I second that. Added.

Oren.


>> Cc: orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org
>> Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
> Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
>> ---
>>  checkpoint/restart.c |    7 +++++++
>>  1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
>> index adebc1c..8958ec7 100644
>> --- a/checkpoint/restart.c
>> +++ b/checkpoint/restart.c
>> @@ -13,6 +13,7 @@
>>  #include <linux/wait.h>
>>  #include <linux/file.h>
>>  #include <linux/magic.h>
>> +#include <linux/personality.h>
>>  #include <linux/checkpoint.h>
>>  #include <linux/checkpoint_hdr.h>
>>
>> @@ -535,12 +536,18 @@ static int do_restart_root(struct cr_ctx *ctx, pid_t pid)
>>  int do_restart(struct cr_ctx *ctx, pid_t pid)
>>  {
>>  	int ret;
>> +	unsigned int original_personality;
>> +	
>> +	original_personality = current->personality;
>> +	current->personality &= ~READ_IMPLIES_EXEC;
>>
>>  	if (ctx)
>>  		ret = do_restart_root(ctx, pid);
>>  	else
>>  		ret = do_restart_task(pid);
>>
>> +	current->personality = original_personality;
>> +
>>  	/* on success, adjust the return value if needed [TODO] */
>>  	return ret;
>>  }
>> -- 
>> 1.6.1
>>
>> _______________________________________________
>> Containers mailing list
>> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
>> https://lists.linux-foundation.org/mailman/listinfo/containers
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linux-foundation.org/mailman/listinfo/containers
> 

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Oren Laadan]

Oren Laadan wrote:
> 
> Serge E. Hallyn wrote:
>> Quoting Dan Smith (danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org):
>>> On s390, all tasks have READ_IMPLIES_EXEC set in current->personality,
>>> which causes the restart process to map things like the stack and heap as
>>> executable.  During the restart process, remove this bit and restore the
>>> original personality afterwards.
>>>
>>> This seems a little ugly, but I don't know that there's a better place for
>>> it.
>> Well imo the only other thing to do would be to do the same thing but
>> just around the main restart_memory function.
>>
> 
> I second that. Added.
> 

In fact, if elsewhere we restore current->personality of the task,
then unless we move it to cr_read_mm(), it will overwrite it :(

Oren.

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Dan Smith]

OL> In fact, if elsewhere we restore current->personality of the task,
OL> then unless we move it to cr_read_mm(), it will overwrite it :(

Should we move it or just remove RIE before we start the restart and
let the task regain the flag if it had it before?

-- 
Dan Smith
IBM Linux Technology Center
email: danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Oren Laadan]

Probably best is to (a) save and restore the task's personality
(regardless), and (b) in do_restart() (re)set the personality as
we wish, with a clear comment about why and the fact that the
'real' personality is restore later.

Oren.

Dan Smith wrote:
> OL> In fact, if elsewhere we restore current->personality of the task,
> OL> then unless we move it to cr_read_mm(), it will overwrite it :(
> 
> Should we move it or just remove RIE before we start the restart and
> let the task regain the flag if it had it before?
> 

Re: [PATCH] Remove READ_IMPLIES_EXEC during restart

[Oren Laadan]

Dan,

Now after the rework of the patchset, it's probably a good time
to add support for this.

I'm unsure if the personality can affect other restore actions
that take place elsewhere If so, probably the correct way is to:

1) restore personality as part of the task (in the beginning)

2) temporarily change it around those places where we want the
"native" personality, e.g. the call to do_mmap_pgoff(), or shmat(),

(The reason not to put it around the entire restore_mm() is to
be safe in case a personality makes a difference when you open
files. This way we isolate the effect of changing personality).

Any thoughts ?

Oren.

Dan Smith wrote:
> OL> In fact, if elsewhere we restore current->personality of the task,
> OL> then unless we move it to cr_read_mm(), it will overwrite it :(
> 
> Should we move it or just remove RIE before we start the restart and
> let the task regain the flag if it had it before?
>