Re: [PATCH 04/11] powerpc: Don't negate error in syscall_set_return_value()

2015-07-27 Thread Kees Cook 
On Thu, Jul 23, 2015 at 3:21 AM, Michael Ellerman m...@ellerman.id.au wrote:
 Currently the only caller of syscall_set_return_value() is seccomp
 filter, which is not enabled on powerpc.

 This means we have not noticed that our implementation of
 syscall_set_return_value() negates error, even though the value passed
 in is already negative.

 So remove the negation in syscall_set_return_value(), and expect the
 caller to do it like all other implementations do.

 Also add a comment about the ccr handling.

 Signed-off-by: Michael Ellerman m...@ellerman.id.au

Reviewed-by: Kees Cook keesc...@chromium.org

-Kees

 ---
  arch/powerpc/include/asm/syscall.h | 8 +++-
  1 file changed, 7 insertions(+), 1 deletion(-)

 diff --git a/arch/powerpc/include/asm/syscall.h 
 b/arch/powerpc/include/asm/syscall.h
 index c6239dabcfb1..cabe90133e69 100644
 --- a/arch/powerpc/include/asm/syscall.h
 +++ b/arch/powerpc/include/asm/syscall.h
 @@ -44,9 +44,15 @@ static inline void syscall_set_return_value(struct 
 task_struct *task,
 struct pt_regs *regs,
 int error, long val)
  {
 +   /*
 +* In the general case it's not obvious that we must deal with CCR
 +* here, as the syscall exit path will also do that for us. However
 +* there are some places, eg. the signal code, which check ccr to
 +* decide if the value in r3 is actually an error.
 +*/
 if (error) {
 regs-ccr |= 0x1000L;
 -   regs-gpr[3] = -error;
 +   regs-gpr[3] = error;
 } else {
 regs-ccr = ~0x1000L;
 regs-gpr[3] = val;
 --
 2.1.0




-- 
Kees Cook
Chrome OS Security
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[PATCH 04/11] powerpc: Don't negate error in syscall_set_return_value()

2015-07-23 Thread Michael Ellerman 
Currently the only caller of syscall_set_return_value() is seccomp
filter, which is not enabled on powerpc.

This means we have not noticed that our implementation of
syscall_set_return_value() negates error, even though the value passed
in is already negative.

So remove the negation in syscall_set_return_value(), and expect the
caller to do it like all other implementations do.

Also add a comment about the ccr handling.

Signed-off-by: Michael Ellerman m...@ellerman.id.au
---
 arch/powerpc/include/asm/syscall.h | 8 +++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/syscall.h 
b/arch/powerpc/include/asm/syscall.h
index c6239dabcfb1..cabe90133e69 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -44,9 +44,15 @@ static inline void syscall_set_return_value(struct 
task_struct *task,
struct pt_regs *regs,
int error, long val)
 {
+   /*
+* In the general case it's not obvious that we must deal with CCR
+* here, as the syscall exit path will also do that for us. However
+* there are some places, eg. the signal code, which check ccr to
+* decide if the value in r3 is actually an error.
+*/
if (error) {
regs-ccr |= 0x1000L;
-   regs-gpr[3] = -error;
+   regs-gpr[3] = error;
} else {
regs-ccr = ~0x1000L;
regs-gpr[3] = val;
-- 
2.1.0

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