[PATCH v2 1/3] arm64: ptrace: Add is_syscall_success to handle compat

[PATCH v2 1/3] arm64: ptrace: Add is_syscall_success to handle compat

[He Zhe]

The general version of is_syscall_success does not handle 32-bit
compatible case, which would cause 32-bit negative return code to be
recoganized as a positive number later and seen as a "success".

Since syscall_get_return_value is defined in syscall.h, implementing
is_syscall_success in ptrace.h would introduce build failure due to
recursive inclusion of some basic headers like mutex.h. Let's put the
implementation to ptrace.c

Signed-off-by: He Zhe <zhe.he@windriver.com>
---
v1 to v2: Call syscall_get_return_value to reduce code duplication

 arch/arm64/include/asm/ptrace.h | 3 +++
 arch/arm64/kernel/ptrace.c      | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index e58bca832dff..3c415e9e5d85 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -328,6 +328,9 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
 	regs->regs[0] = rc;
 }
 
+extern inline int is_syscall_success(struct pt_regs *regs);
+#define is_syscall_success(regs) is_syscall_success(regs)
+
 /**
  * regs_get_kernel_argument() - get Nth function argument in kernel
  * @regs:	pt_regs of that context
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 170f42fd6101..2c84255e1e41 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1909,3 +1909,8 @@ int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task)
 	else
 		return valid_native_regs(regs);
 }
+
+inline int is_syscall_success(struct pt_regs *regs)
+{
+	return !IS_ERR_VALUE(syscall_get_return_value(current, regs));
+}
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v2 2/3] arm64: syscall.h: Add sign extension handling in syscall_get_return_value for compat

[He Zhe]

Add sign extension handling in syscall_get_return_value so that it can
handle 32-bit compatible case and can be used by for example audit, just
like what syscall_get_error does.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
v1 to v2: Improve error code check suggested by Mark

 arch/arm64/include/asm/syscall.h | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index cfc0672013f6..c3b5fca82ff4 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -44,7 +44,20 @@ static inline long syscall_get_error(struct task_struct *task,
 static inline long syscall_get_return_value(struct task_struct *task,
 					    struct pt_regs *regs)
 {
-	return regs->regs[0];
+	long val = regs->regs[0];
+	long error = val;
+
+	if (compat_user_mode(regs))
+		error = sign_extend64(error, 31);
+
+	/*
+	 * Return codes with bit 31 set may or may not be an error code.
+	 * For example, mmap may return a legal 32 bit address with bit 31 set
+	 * for 32 bit thread, in which case the untouched val should be
+	 * returned. Otherwise, the sign-extended error should be returned if
+	 * it still falls in error number range.
+	 */
+	return IS_ERR_VALUE(error) ? error : val;
 }
 
 static inline void syscall_set_return_value(struct task_struct *task,
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[He Zhe]

regs_return_value for some architectures like arm64 simply retrieve
register value from pt_regs without sign extension in 32-bit compatible
case and cause audit to have false syscall return code. For example,
32-bit -13 would be treated as 4294967283 below.

type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
success=yes exit=4294967283

We just added proper sign extension in syscall_get_return_value which
should be used instead.

Signed-off-by: He Zhe <zhe.he@windriver.com>
---
v1 to v2: No change

 include/linux/audit.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 82b7c1116a85..135adbe22c19 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
 {
 	if (unlikely(audit_context())) {
 		int success = is_syscall_success(pt_regs);
-		long return_code = regs_return_value(pt_regs);
+		long return_code = syscall_get_return_value(current, pt_regs);
 
 		__audit_syscall_exit(success, return_code);
 	}
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 2/3] arm64: syscall.h: Add sign extension handling in syscall_get_return_value for compat

[Mark Rutland]

Hi,

On Fri, Apr 23, 2021 at 06:35:32PM +0800, He Zhe wrote:
> Add sign extension handling in syscall_get_return_value so that it can
> handle 32-bit compatible case and can be used by for example audit, just
> like what syscall_get_error does.
> 
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> v1 to v2: Improve error code check suggested by Mark
> 
>  arch/arm64/include/asm/syscall.h | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
> index cfc0672013f6..c3b5fca82ff4 100644
> --- a/arch/arm64/include/asm/syscall.h
> +++ b/arch/arm64/include/asm/syscall.h
> @@ -44,7 +44,20 @@ static inline long syscall_get_error(struct task_struct *task,
>  static inline long syscall_get_return_value(struct task_struct *task,
>  					    struct pt_regs *regs)
>  {
> -	return regs->regs[0];
> +	long val = regs->regs[0];
> +	long error = val;
> +
> +	if (compat_user_mode(regs))
> +		error = sign_extend64(error, 31);
> +
> +	/*
> +	 * Return codes with bit 31 set may or may not be an error code.
> +	 * For example, mmap may return a legal 32 bit address with bit 31 set
> +	 * for 32 bit thread, in which case the untouched val should be
> +	 * returned. Otherwise, the sign-extended error should be returned if
> +	 * it still falls in error number range.
> +	 */
> +	return IS_ERR_VALUE(error) ? error : val;

I'm afraid I have misled you here.

I wrote up a test that uses PTRACE_GET_SYSCALL_INFO, and I found that on
a 32-bit arm (v5.12) kernel, *all* syscall return values get
sign-extended after all. For example, if (on a 32-bit kernel) I use
MAP_FIXED to mmap() at address 0x8bad0000, the return value reported in
ptrace_syscall_info::exit::rval is 0xffffffff8bad0000.

So for that we shoudn't have the IS_ERR_VALUE() check after all, but I'm
not currently sure whether there are other cases where 32-bit arm
wouldn't sign-extend, and I think we'll need to dig into this some more.

Thanks,
Mark.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[Paul Moore]

On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@windriver.com> wrote:
>
> regs_return_value for some architectures like arm64 simply retrieve
> register value from pt_regs without sign extension in 32-bit compatible
> case and cause audit to have false syscall return code. For example,
> 32-bit -13 would be treated as 4294967283 below.
>
> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
> success=yes exit=4294967283
>
> We just added proper sign extension in syscall_get_return_value which
> should be used instead.
>
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> v1 to v2: No change
>
>  include/linux/audit.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Perhaps I missed it but did you address the compile error that was
found by the kernel test robot?

Regardless, one comment inline below ...

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 82b7c1116a85..135adbe22c19 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
>  {
>         if (unlikely(audit_context())) {
>                 int success = is_syscall_success(pt_regs);

Since we are shifting to use syscall_get_return_value() below, would
it also make sense to shift to using syscall_get_error() here instead
of is_syscall_success()?

> -               long return_code = regs_return_value(pt_regs);
> +               long return_code = syscall_get_return_value(current, pt_regs);
>
>                 __audit_syscall_exit(success, return_code);
>         }

-- 
paul moore
www.paul-moore.com

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[He Zhe]

On 5/11/21 6:38 AM, Paul Moore wrote:
> On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@windriver.com> wrote:
>> regs_return_value for some architectures like arm64 simply retrieve
>> register value from pt_regs without sign extension in 32-bit compatible
>> case and cause audit to have false syscall return code. For example,
>> 32-bit -13 would be treated as 4294967283 below.
>>
>> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
>> success=yes exit=4294967283
>>
>> We just added proper sign extension in syscall_get_return_value which
>> should be used instead.
>>
>> Signed-off-by: He Zhe <zhe.he@windriver.com>
>> ---
>> v1 to v2: No change
>>
>>  include/linux/audit.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> Perhaps I missed it but did you address the compile error that was
> found by the kernel test robot?

I sent a patch adding syscall_get_return_value for alpha to fix this bot warning.
https://lore.kernel.org/lkml/20210426091629.45020-1-zhe.he@windriver.com/
which can be found in this mail thread.

>
> Regardless, one comment inline below ...
>
>> diff --git a/include/linux/audit.h b/include/linux/audit.h
>> index 82b7c1116a85..135adbe22c19 100644
>> --- a/include/linux/audit.h
>> +++ b/include/linux/audit.h
>> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
>>  {
>>         if (unlikely(audit_context())) {
>>                 int success = is_syscall_success(pt_regs);
> Since we are shifting to use syscall_get_return_value() below, would
> it also make sense to shift to using syscall_get_error() here instead
> of is_syscall_success()?

In [PATCH v2 1/3], is_syscall_success calls syscall_get_return_value to take
care of the sign extension issue. Keeping using is_syscall_success is to not
potentially changing other architectures' behavior.

Thanks,
Zhe

>
>> -               long return_code = regs_return_value(pt_regs);
>> +               long return_code = syscall_get_return_value(current, pt_regs);
>>
>>                 __audit_syscall_exit(success, return_code);
>>         }


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[Paul Moore]

On Mon, May 10, 2021 at 11:19 PM He Zhe <zhe.he@windriver.com> wrote:
> On 5/11/21 6:38 AM, Paul Moore wrote:
> > On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@windriver.com> wrote:
> >> regs_return_value for some architectures like arm64 simply retrieve
> >> register value from pt_regs without sign extension in 32-bit compatible
> >> case and cause audit to have false syscall return code. For example,
> >> 32-bit -13 would be treated as 4294967283 below.
> >>
> >> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
> >> success=yes exit=4294967283
> >>
> >> We just added proper sign extension in syscall_get_return_value which
> >> should be used instead.
> >>
> >> Signed-off-by: He Zhe <zhe.he@windriver.com>
> >> ---
> >> v1 to v2: No change
> >>
> >>  include/linux/audit.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Perhaps I missed it but did you address the compile error that was
> > found by the kernel test robot?
>
> I sent a patch adding syscall_get_return_value for alpha to fix this bot warning.
> https://lore.kernel.org/lkml/20210426091629.45020-1-zhe.he@windriver.com/
> which can be found in this mail thread.

At the very least you should respin the patchset with the alpha fix
included in the patchset; it's a bit messy otherwise.

> >> diff --git a/include/linux/audit.h b/include/linux/audit.h
> >> index 82b7c1116a85..135adbe22c19 100644
> >> --- a/include/linux/audit.h
> >> +++ b/include/linux/audit.h
> >> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
> >>  {
> >>         if (unlikely(audit_context())) {
> >>                 int success = is_syscall_success(pt_regs);
> >
> > Since we are shifting to use syscall_get_return_value() below, would
> > it also make sense to shift to using syscall_get_error() here instead
> > of is_syscall_success()?
>
> In [PATCH v2 1/3], is_syscall_success calls syscall_get_return_value to take
> care of the sign extension issue. Keeping using is_syscall_success is to not
> potentially changing other architectures' behavior.

That was only for aarch64, right?  What about all the other
architectures?  The comment block for syscall_get_return_value()
advises that syscall_get_error() should be used and that appears to be
what is done in the ptrace code.

-- 
paul moore
www.paul-moore.com

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[He Zhe]

On 5/11/21 10:51 PM, Paul Moore wrote:
> On Mon, May 10, 2021 at 11:19 PM He Zhe <zhe.he@windriver.com> wrote:
>> On 5/11/21 6:38 AM, Paul Moore wrote:
>>> On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@windriver.com> wrote:
>>>> regs_return_value for some architectures like arm64 simply retrieve
>>>> register value from pt_regs without sign extension in 32-bit compatible
>>>> case and cause audit to have false syscall return code. For example,
>>>> 32-bit -13 would be treated as 4294967283 below.
>>>>
>>>> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
>>>> success=yes exit=4294967283
>>>>
>>>> We just added proper sign extension in syscall_get_return_value which
>>>> should be used instead.
>>>>
>>>> Signed-off-by: He Zhe <zhe.he@windriver.com>
>>>> ---
>>>> v1 to v2: No change
>>>>
>>>>  include/linux/audit.h | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>> Perhaps I missed it but did you address the compile error that was
>>> found by the kernel test robot?
>> I sent a patch adding syscall_get_return_value for alpha to fix this bot warning.
>> https://lore.kernel.org/lkml/20210426091629.45020-1-zhe.he@windriver.com/
>> which can be found in this mail thread.
> At the very least you should respin the patchset with the alpha fix
> included in the patchset; it's a bit messy otherwise.
>
>>>> diff --git a/include/linux/audit.h b/include/linux/audit.h
>>>> index 82b7c1116a85..135adbe22c19 100644
>>>> --- a/include/linux/audit.h
>>>> +++ b/include/linux/audit.h
>>>> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
>>>>  {
>>>>         if (unlikely(audit_context())) {
>>>>                 int success = is_syscall_success(pt_regs);
>>> Since we are shifting to use syscall_get_return_value() below, would
>>> it also make sense to shift to using syscall_get_error() here instead
>>> of is_syscall_success()?
>> In [PATCH v2 1/3], is_syscall_success calls syscall_get_return_value to take
>> care of the sign extension issue. Keeping using is_syscall_success is to not
>> potentially changing other architectures' behavior.
> That was only for aarch64, right?  What about all the other
> architectures?  The comment block for syscall_get_return_value()
> advises that syscall_get_error() should be used and that appears to be
> what is done in the ptrace code.

Yes, it was only for aarch64. No similar issue hasn't observed for other
architectures on my side, so I was trying to minimize the impact.

The "comment block" you mentioned is the following line, right?
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/asm-generic/syscall.h#n77
[PATCH v2 2/3] was used to cover this concern. But as we can see in
Mark Rutland's last reply, there'are more things to be considered and we are
still trying to find a proper solution.

Thanks,
Zhe

>


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 3/3] audit: Use syscall_get_return_value to get syscall return code in audit_syscall_exit

[Paul Moore]

On Wed, May 12, 2021 at 4:43 AM He Zhe <zhe.he@windriver.com> wrote:
> On 5/11/21 10:51 PM, Paul Moore wrote:
> > On Mon, May 10, 2021 at 11:19 PM He Zhe <zhe.he@windriver.com> wrote:
> >> On 5/11/21 6:38 AM, Paul Moore wrote:
> >>> On Fri, Apr 23, 2021 at 6:36 AM He Zhe <zhe.he@windriver.com> wrote:
> >>>> regs_return_value for some architectures like arm64 simply retrieve
> >>>> register value from pt_regs without sign extension in 32-bit compatible
> >>>> case and cause audit to have false syscall return code. For example,
> >>>> 32-bit -13 would be treated as 4294967283 below.
> >>>>
> >>>> type=SYSCALL msg=audit(1611110715.887:582): arch=40000028 syscall=322
> >>>> success=yes exit=4294967283
> >>>>
> >>>> We just added proper sign extension in syscall_get_return_value which
> >>>> should be used instead.
> >>>>
> >>>> Signed-off-by: He Zhe <zhe.he@windriver.com>
> >>>> ---
> >>>> v1 to v2: No change
> >>>>
> >>>>  include/linux/audit.h | 2 +-
> >>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>> Perhaps I missed it but did you address the compile error that was
> >>> found by the kernel test robot?
> >> I sent a patch adding syscall_get_return_value for alpha to fix this bot warning.
> >> https://lore.kernel.org/lkml/20210426091629.45020-1-zhe.he@windriver.com/
> >> which can be found in this mail thread.
> > At the very least you should respin the patchset with the alpha fix
> > included in the patchset; it's a bit messy otherwise.
> >
> >>>> diff --git a/include/linux/audit.h b/include/linux/audit.h
> >>>> index 82b7c1116a85..135adbe22c19 100644
> >>>> --- a/include/linux/audit.h
> >>>> +++ b/include/linux/audit.h
> >>>> @@ -334,7 +334,7 @@ static inline void audit_syscall_exit(void *pt_regs)
> >>>>  {
> >>>>         if (unlikely(audit_context())) {
> >>>>                 int success = is_syscall_success(pt_regs);
> >>> Since we are shifting to use syscall_get_return_value() below, would
> >>> it also make sense to shift to using syscall_get_error() here instead
> >>> of is_syscall_success()?
> >> In [PATCH v2 1/3], is_syscall_success calls syscall_get_return_value to take
> >> care of the sign extension issue. Keeping using is_syscall_success is to not
> >> potentially changing other architectures' behavior.
> > That was only for aarch64, right?  What about all the other
> > architectures?  The comment block for syscall_get_return_value()
> > advises that syscall_get_error() should be used and that appears to be
> > what is done in the ptrace code.
>
> Yes, it was only for aarch64. No similar issue hasn't observed for other
> architectures on my side, so I was trying to minimize the impact.
>
> The "comment block" you mentioned is the following line, right?
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/asm-generic/syscall.h#n77
> [PATCH v2 2/3] was used to cover this concern. But as we can see in
> Mark Rutland's last reply, there'are more things to be considered and we are
> still trying to find a proper solution.

It sounds like you are going to be submitting another patchset at some
point in the future - that's good - when you do please use
syscall_get_error() in conjunction with syscall_get_return_value() or
explain why doing so is wrong.  The explanation should be in a code
comment, not just an email and/or commit description.

-- 
paul moore
www.paul-moore.com

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel