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

Thomas Bogendoerfer
2020-12-29T15:10:37Z

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@kernel.org # v3.7+
> Signed-off-by: Al Viro <viro@zeniv.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.

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