[mips] Fix indirect syscall tracing & seccomp filtering for big endian MIPS64 kernels with 32-bit userland.

debian/changelog

@@ -827,6 +827,10 @@ linux (4.19.34-1) UNRELEASED; urgency=medium
   * ACPICA: Namespace: remove address node from global list after method
     termination
 
+  [ Aurelien Jarno ]
+  * [mips] Fix indirect syscall tracing & seccomp filtering for big endian
+    MIPS64 kernels with 32-bit userland.
+
  -- Ben Hutchings <ben@decadent.org.uk>  Mon, 18 Mar 2019 22:50:08 +0000
 
 linux (4.19.28-2) unstable; urgency=medium

debian/patches/bugfix/mips/MIPS-scall64-o32-Fix-indirect-syscall-number-load.patch

@@ -0,0 +1,52 @@
+From: Aurelien Jarno <aurelien@aurel32.net>
+Date: Tue, 9 Apr 2019 16:53:55 +0200
+Subject: MIPS: scall64-o32: Fix indirect syscall number load
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+Origin: https://git.kernel.org/linus/79b4a9cf0e2ea8203ce777c8d5cfa86c71eae86e
+
+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+
+Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
+Signed-off-by: Paul Burton <paul.burton@mips.com>
+Cc: Ralf Baechle <ralf@linux-mips.org>
+Cc: James Hogan <jhogan@kernel.org>
+Cc: linux-mips@vger.kernel.org
+Cc: linux-kernel@vger.kernel.org
+---
+ 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
+-- 
+2.20.1
+

debian/patches/series

@@ -81,6 +81,7 @@ bugfix/arm/ARM-dts-sun8i-h3-add-sy8106a-to-orange-pi-plus.patch
 bugfix/arm64/arm64-dts-allwinner-a64-Enable-A64-timer-workaround.patch
 bugfix/mips/MIPS-Loongson-Introduce-and-use-loongson_llsc_mb.patch
 bugfix/powerpc/powerpc-vdso-make-vdso32-installation-conditional-in.patch
+bugfix/mips/MIPS-scall64-o32-Fix-indirect-syscall-number-load.patch
 
 # Arch features
 features/mips/MIPS-increase-MAX-PHYSMEM-BITS-on-Loongson-3-only.patch