linux-kernel - Re: [PATCH] MIPS: scall64-o32: Fix indirect syscall number load

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Date:   Mon, 15 Apr 2019 17:36:58 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     Aurelien Jarno <aurelien@...el32.net>
CC:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <pburton@...ecomp.com>,
        James Hogan <jhogan@...nel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Aurelien Jarno <aurelien@...el32.net>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH] MIPS: scall64-o32: Fix indirect syscall number load

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 <aurelien@...el32.net>
> Cc: <stable@...r.kernel.org> # v3.15+
> Reviewed-by: Philippe Mathieu-DaudÃ© <f4bug@...at.org>

Applied to mips-fixes.

Thanks,
    Paul

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