[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20200422143526.GD54796@lakrids.cambridge.arm.com>
Date: Wed, 22 Apr 2020 15:35:27 +0100
From: Mark Rutland <mark.rutland@....com>
To: Phong Tran <tranmanphong@...il.com>
Cc: steve.capper@....com, steven.price@....com, will@...nel.org,
keescook@...omium.org, greg@...ah.com, akpm@...ux-foundation.org,
alexios.zavras@...el.com, broonie@...nel.org,
kernel-hardening@...ts.openwall.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
tglx@...utronix.de
Subject: Re: [PATCH v2] arm64: add check_wx_pages debugfs for CHECK_WX
On Wed, Apr 22, 2020 at 12:35:58AM +0700, Phong Tran wrote:
> follow the suggestion from
> https://github.com/KSPP/linux/issues/35
>
> Signed-off-by: Phong Tran <tranmanphong@...il.com>
> ---
> Change since v1:
> - Update the Kconfig help text
> - Don't check the return value of debugfs_create_file()
> - Tested on QEMU aarch64
As on v1, I think that this should be generic across all architectures
with CONFIG_DEBUG_WX. Adding this only on arm64 under
CONFIG_PTDUMP_DEBUGFS (which does not generally imply a WX check)
doesn't seem right.
Maybe we need a new ARCH_HAS_CHECK_WX config to make that simpler, but
that seems simple to me.
Thanks,
Marm.
> root@...uarm64:~# zcat /proc/config.gz | grep PTDUMP
> CONFIG_GENERIC_PTDUMP=y
> CONFIG_PTDUMP_CORE=y
> CONFIG_PTDUMP_DEBUGFS=y
> root@...uarm64:~# uname -a
> Linux qemuarm64 5.7.0-rc2-00001-g20ddb383c313 #3 SMP PREEMPT Tue Apr 21 23:18:56 +07 2020 aarch64 GNU/Linux
> root@...uarm64:~# echo 1 > /sys/kernel/debug/check_wx_pages
> [ 63.261868] Checked W+X mappings: passed, no W+X pages found
> ---
> arch/arm64/Kconfig.debug | 5 ++++-
> arch/arm64/include/asm/ptdump.h | 2 ++
> arch/arm64/mm/dump.c | 1 +
> arch/arm64/mm/ptdump_debugfs.c | 18 ++++++++++++++++++
> 4 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index a1efa246c9ed..cd82c9d3664a 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -48,7 +48,10 @@ config DEBUG_WX
> of other unfixed kernel bugs easier.
>
> There is no runtime or memory usage effect of this option
> - once the kernel has booted up - it's a one time check.
> + once the kernel has booted up - it's a one time check at
> + boot, and can also be triggered at runtime by echo "1" to
> + "check_wx_pages". The "check_wx_pages" is available only with
> + CONFIG_PTDUMP_DEBUGFS is enabled.
>
> If in doubt, say "Y".
>
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 38187f74e089..c90a6ec6f59b 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -24,9 +24,11 @@ struct ptdump_info {
> void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> #ifdef CONFIG_PTDUMP_DEBUGFS
> void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> +void ptdump_check_wx_init(void);
> #else
> static inline void ptdump_debugfs_register(struct ptdump_info *info,
> const char *name) { }
> +static inline void ptdump_check_wx_init(void) { }
> #endif
> void ptdump_check_wx(void);
> #endif /* CONFIG_PTDUMP_CORE */
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 860c00ec8bd3..60c99a047763 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -378,6 +378,7 @@ static int ptdump_init(void)
> #endif
> ptdump_initialize();
> ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
> + ptdump_check_wx_init();
> return 0;
> }
> device_initcall(ptdump_init);
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index d29d722ec3ec..6b0aa16cb17b 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -20,3 +20,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
> {
> debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> }
> +
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> + if (val != 1ULL)
> + return -EINVAL;
> +
> + ptdump_check_wx();
> +
> + return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +void ptdump_check_wx_init(void)
> +{
> + debugfs_create_file("check_wx_pages", 0200, NULL,
> + NULL, &check_wx_fops) ? 0 : -ENOMEM;
> +}
> --
> 2.20.1
>
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
