[PATCH] s390/seccomp: fix error return for filtered system calls

[PATCH] s390/seccomp: fix error return for filtered system calls

[Michael Holzheu]

commit dc295880c6752076f8b94ba3885d0bfff09e3e82 upstream

The syscall_set_return_value function of s390 negates the error argument
before storing the value to the return register gpr2. This is incorrect,
the seccomp code already passes the negative error value.
Store the unmodified error value to gpr2.

Signed-off-by: Jan Willeke <willeke@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
* Requested versions for stable: v2.6.28 - v3.16
* Justification: Patch is needed e.g. for Docker seccomp support on
  kernels with version < 3.17.
* Bug was introduced by commit: 753c4dd6a2fa2af "[S390] ptrace changes" 
---
 arch/s390/include/asm/syscall.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/syscall.h
b/arch/s390/include/asm/syscall.h index abad78d..5bc1259 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -54,7 +54,7 @@ static inline void syscall_set_return_value(struct
task_struct *task, struct pt_regs *regs,
 					    int error, long val)
 {
-	regs->gprs[2] = error ? -error : val;
+	regs->gprs[2] = error ? error : val;
 }
 
 static inline void syscall_get_arguments(struct task_struct *task,
-- 
2.6.6

Re: [PATCH] s390/seccomp: fix error return for filtered system calls

[Ben Hutchings]

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On Mon, 2016-07-25 at 16:16 +0200, Michael Holzheu wrote:
> commit dc295880c6752076f8b94ba3885d0bfff09e3e82 upstream
> 
> The syscall_set_return_value function of s390 negates the error argument
> before storing the value to the return register gpr2. This is incorrect,
> the seccomp code already passes the negative error value.
> Store the unmodified error value to gpr2.
> 
> Signed-off-by: Jan Willeke <willeke@de.ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> ---
> * Requested versions for stable: v2.6.28 - v3.16

Belatedly queued this up for 3.16.

Ben.

> * Justification: Patch is needed e.g. for Docker seccomp support on
>   kernels with version < 3.17.
> * Bug was introduced by commit: 753c4dd6a2fa2af "[S390] ptrace changes" 
> ---
>  arch/s390/include/asm/syscall.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/syscall.h
> b/arch/s390/include/asm/syscall.h index abad78d..5bc1259 100644
> --- a/arch/s390/include/asm/syscall.h
> +++ b/arch/s390/include/asm/syscall.h
> @@ -54,7 +54,7 @@ static inline void syscall_set_return_value(struct
> task_struct *task, struct pt_regs *regs,
>  					    int error, long val)
>  {
> -	regs->gprs[2] = error ? -error : val;
> +	regs->gprs[2] = error ? error : val;
>  }
>  
>  static inline void syscall_get_arguments(struct task_struct *task,
-- 
Ben Hutchings
compatible: Gracefully accepts erroneous data from any source


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