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@xxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # 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@xxxxxxxxx>
