queue-4.4/mips-scall64-o32-fix-indirect-syscall-number-load.patch

   1 From 79b4a9cf0e2ea8203ce777c8d5cfa86c71eae86e Mon Sep 17 00:00:00 2001
   2 From: Aurelien Jarno <aurelien@aurel32.net>
   3 Date: Tue, 9 Apr 2019 16:53:55 +0200
   4 Subject: MIPS: scall64-o32: Fix indirect syscall number load
   5 MIME-Version: 1.0
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   8
   9 From: Aurelien Jarno <aurelien@aurel32.net>
  10
  11 commit 79b4a9cf0e2ea8203ce777c8d5cfa86c71eae86e upstream.
  12
  13 Commit 4c21b8fd8f14 (MIPS: seccomp: Handle indirect system calls (o32))
  14 added indirect syscall detection for O32 processes running on MIPS64,
  15 but it did not work correctly for big endian kernel/processes. The
  16 reason is that the syscall number is loaded from ARG1 using the lw
  17 instruction while this is a 64-bit value, so zero is loaded instead of
  18 the syscall number.
  19
  20 Fix the code by using the ld instruction instead. When running a 32-bit
  21 processes on a 64 bit CPU, the values are properly sign-extended, so it
  22 ensures the value passed to syscall_trace_enter is correct.
  23
  24 Recent systemd versions with seccomp enabled whitelist the getpid
  25 syscall for their internal  processes (e.g. systemd-journald), but call
  26 it through syscall(SYS_getpid). This fix therefore allows O32 big endian
  27 systems with a 64-bit kernel to run recent systemd versions.
  28
  29 Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
  30 Cc: <stable@vger.kernel.org> # v3.15+
  31 Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
  32 Signed-off-by: Paul Burton <paul.burton@mips.com>
  33 Cc: Ralf Baechle <ralf@linux-mips.org>
  34 Cc: James Hogan <jhogan@kernel.org>
  35 Cc: linux-mips@vger.kernel.org
  36 Cc: linux-kernel@vger.kernel.org
  37 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  38
  39 ---
  40  arch/mips/kernel/scall64-o32.S |    2 +-
  41  1 file changed, 1 insertion(+), 1 deletion(-)
  42
  43 --- a/arch/mips/kernel/scall64-o32.S
  44 +++ b/arch/mips/kernel/scall64-o32.S
  45 @@ -126,7 +126,7 @@ trace_a_syscall:
  46         subu    t1, v0,  __NR_O32_Linux
  47         move    a1, v0
  48         bnez    t1, 1f /* __NR_syscall at offset 0 */
  49 -       lw      a1, PT_R4(sp) /* Arg1 for __NR_syscall case */
  50 +       ld      a1, PT_R4(sp) /* Arg1 for __NR_syscall case */
  51         .set    pop
  52
  53  1:     jal     syscall_trace_enter