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Message-ID: <20160513092419.GA13689@arm.com>
Date: Fri, 13 May 2016 10:24:20 +0100
From: Will Deacon <will.deacon@....com>
To: Yury Norov <ynorov@...iumnetworks.com>
Cc: arnd@...db.de, catalin.marinas@....com,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: fix current_thread_info()->addr_limit setup
On Thu, May 12, 2016 at 02:26:54PM +0300, Yury Norov wrote:
> At elf loading in flush_old_exec() in fs/exec.c, generic code sets
> current_thread_info()->addr_limit to one that corresponds aarch64 value,
> and ignores compat mode there as corresponding status setup happens
> later on in load_elf_binary() by SET_PERSONALITY() macro. As result,
> compat task has wrong addr_limit, and it may cause various bugs.
>
> This patch fixes it. It also fixes USER_DS macro to return different
> values depending on compat at runtime.
>
> It was discovered during ilp32 development. See details here:
> https://lkml.org/lkml/2016/5/11/975
It looks like that thread is ongoing, with discussion around a generic
fix and a related issue with our TLS handling:
https://lkml.org/lkml/2016/5/12/513
https://lkml.org/lkml/2016/5/12/515
so I'm going to hold off on this until there's some agreement on the
right way forward. Whatever we end up doing, we should probably cc
stable too.
> Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> ---
> arch/arm64/include/asm/elf.h | 11 +++++++++--
> arch/arm64/include/asm/uaccess.h | 2 +-
> 2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 24ed037..fda75ce 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -138,7 +138,10 @@ typedef struct user_fpsimd_state elf_fpregset_t;
> */
> #define ELF_PLAT_INIT(_r, load_addr) (_r)->regs[0] = 0
>
> -#define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT);
> +#define SET_PERSONALITY(ex) do { \
> + clear_thread_flag(TIF_32BIT); \
> + set_fs(TASK_SIZE_64); \
You could just use USER_DS for both of the SET_PERSONALITY macros.
Will
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