Re: [PATCH 04/11] powerpc: Don't negate error in syscall_set_return_value()
From: Kees Cook <hidden>
Date: 2015-07-27 18:49:54
Also in:
lkml
On Thu, Jul 23, 2015 at 3:21 AM, Michael Ellerman [off-list ref] 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 <mpe@ellerman.id.au>
Reviewed-by: Kees Cook <redacted> -Kees
quoted hunk ↗ jump to hunk
--- 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 |= 0x10000000L; - regs->gpr[3] = -error; + regs->gpr[3] = error; } else { regs->ccr &= ~0x10000000L; regs->gpr[3] = val; --2.1.0
-- Kees Cook Chrome OS Security