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 <[email protected]>
Cc: <[email protected]> # 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
--
2.20.1
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 <[email protected]>
> Cc: <[email protected]> # 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 <[email protected]>
Hello,
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 <[email protected]>
> Cc: <[email protected]> # v3.15+
> Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Applied to mips-fixes.
Thanks,
Paul
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