linux-kernel - Re: [RFC][PATCH] NT_FILE/NT_SIGINFO breakage on mips compat coredumps

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Message-ID: <20201229150924.GB7832@alpha.franken.de>
Date:   Tue, 29 Dec 2020 16:09:25 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     "Maciej W. Rozycki" <macro@...ux-mips.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        linux-mips@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>,
        Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [RFC][PATCH] NT_FILE/NT_SIGINFO breakage on mips compat coredumps

On Thu, Dec 24, 2020 at 07:44:38PM +0000, Al Viro wrote:
> [mips] fix malformed NT_FILE and NT_SIGINFO in 32bit coredumps
> 
> 	Patches that introduced NT_FILE and NT_SIGINFO notes back in 2012
> had taken care of native (fs/binfmt_elf.c) and compat (fs/compat_binfmt_elf.c)
> coredumps; unfortunately, compat on mips (which does not go through the
> usual compat_binfmt_elf.c) had not been noticed.
> 
> 	As the result, both N32 and O32 coredumps on 64bit mips kernels
> have those sections malformed enough to confuse the living hell out of
> all gdb and readelf versions (up to and including the tip of binutils-gdb.git).
> 
> 	Longer term solution is to make both O32 and N32 compat use the
> regular compat_binfmt_elf.c, but that's too much for backports.  The minimal
> solution is to do in arch/mips/kernel/binfmt_elf[on]32.c the same thing
> those patches have done in fs/compat_binfmt_elf.c
> 
> Cc: stable@...nel.org # v3.7+
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> ---
> diff --git a/arch/mips/kernel/binfmt_elfn32.c b/arch/mips/kernel/binfmt_elfn32.c
> index 6ee3f7218c67..c4441416e96b 100644
> --- a/arch/mips/kernel/binfmt_elfn32.c
> +++ b/arch/mips/kernel/binfmt_elfn32.c
> @@ -103,4 +103,11 @@ jiffies_to_old_timeval32(unsigned long jiffies, struct old_timeval32 *value)
>  #undef ns_to_kernel_old_timeval
>  #define ns_to_kernel_old_timeval ns_to_old_timeval32
>  
> +/*
> + * Some data types as stored in coredump.
> + */
> +#define user_long_t             compat_long_t
> +#define user_siginfo_t          compat_siginfo_t
> +#define copy_siginfo_to_external        copy_siginfo_to_external32
> +
>  #include "../../../fs/binfmt_elf.c"
> diff --git a/arch/mips/kernel/binfmt_elfo32.c b/arch/mips/kernel/binfmt_elfo32.c
> index 6dd103d3cebb..7b2a23f48c1a 100644
> --- a/arch/mips/kernel/binfmt_elfo32.c
> +++ b/arch/mips/kernel/binfmt_elfo32.c
> @@ -106,4 +106,11 @@ jiffies_to_old_timeval32(unsigned long jiffies, struct old_timeval32 *value)
>  #undef ns_to_kernel_old_timeval
>  #define ns_to_kernel_old_timeval ns_to_old_timeval32
>  
> +/*
> + * Some data types as stored in coredump.
> + */
> +#define user_long_t             compat_long_t
> +#define user_siginfo_t          compat_siginfo_t
> +#define copy_siginfo_to_external        copy_siginfo_to_external32
> +
>  #include "../../../fs/binfmt_elf.c"

LGTM, I've applied it to mips-fixes.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]