lkml.org 
[lkml]   [2019]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] MIPS: scall64-o32: Fix indirect syscall number load
From
Date
On 4/9/19 4:53 PM, Aurelien Jarno wrote:
> Commit 4c21b8fd8f14 (MIPS: seccomp: Handle indirect system calls (o32))
> added indirect syscall detection for O32 processes running on MIPS64,
> but it did not work correctly for big endian kernel/processes. The
> reason is that the syscall number is loaded from ARG1 using the lw
> instruction while this is a 64-bit value, so zero is loaded instead of
> the syscall number.
>
> Fix the code by using the ld instruction instead. When running a 32-bit
> processes on a 64 bit CPU, the values are properly sign-extended, so it
> ensures the value passed to syscall_trace_enter is correct.
>
> Recent systemd versions with seccomp enabled whitelist the getpid
> syscall for their internal processes (e.g. systemd-journald), but call
> it through syscall(SYS_getpid). This fix therefore allows O32 big endian
> systems with a 64-bit kernel to run recent systemd versions.
>
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> Cc: <stable@vger.kernel.org> # v3.15+
> ---
> arch/mips/kernel/scall64-o32.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> index f158c5894a9a..feb2653490df 100644
> --- a/arch/mips/kernel/scall64-o32.S
> +++ b/arch/mips/kernel/scall64-o32.S
> @@ -125,7 +125,7 @@ trace_a_syscall:
> subu t1, v0, __NR_O32_Linux
> move a1, v0
> bnez t1, 1f /* __NR_syscall at offset 0 */
> - lw a1, PT_R4(sp) /* Arg1 for __NR_syscall case */
> + ld a1, PT_R4(sp) /* Arg1 for __NR_syscall case */
> .set pop
>
> 1: jal syscall_trace_enter
>
>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

\
 
 \ /
  Last update: 2019-04-14 22:32    [W:0.050 / U:48.132 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site