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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id e9sm1299721pfl.179.2020.03.09.09.15.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2020 09:15:11 -0700 (PDT) Date: Mon, 9 Mar 2020 09:15:10 -0700 From: Kees Cook To: Mark Rutland Cc: Phong Tran , catalin.marinas@arm.com, will@kernel.org, alexios.zavras@intel.com, tglx@linutronix.de, akpm@linux-foundation.org, steven.price@arm.com, steve.capper@arm.com, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [PATCH] arm64: add check_wx_pages debugfs for CHECK_WX Message-ID: <202003090914.F6720CFF13@keescook> References: <20200307093926.27145-1-tranmanphong@gmail.com> <20200309121713.GA26309@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200309121713.GA26309@lakrids.cambridge.arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 09, 2020 at 12:17:14PM +0000, Mark Rutland wrote: > On Sat, Mar 07, 2020 at 04:39:26PM +0700, Phong Tran wrote: > > follow the suggestion from > > https://github.com/KSPP/linux/issues/35 > > That says: > > | This should be implemented for all architectures > > ... so surely this should be in generic code, rahter than being > arm64-specific? Not all architectures have implemented CONFIG_DEBUG_WX... -Kees > > Thanks, > Mark. > > > > > Signed-off-by: Phong Tran > > --- > > arch/arm64/Kconfig.debug | 3 ++- > > arch/arm64/include/asm/ptdump.h | 2 ++ > > arch/arm64/mm/dump.c | 1 + > > arch/arm64/mm/ptdump_debugfs.c | 18 ++++++++++++++++++ > > 4 files changed, 23 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug > > index 1c906d932d6b..be552fa351e2 100644 > > --- a/arch/arm64/Kconfig.debug > > +++ b/arch/arm64/Kconfig.debug > > @@ -48,7 +48,8 @@ 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 and > > + can be checked by echo "1" to "check_wx_pages" debugfs in runtime. > > > > If in doubt, say "Y". > > > > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h > > index 38187f74e089..b80d6b4fc508 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); > > +int ptdump_check_wx_init(void); > > #else > > static inline void ptdump_debugfs_register(struct ptdump_info *info, > > const char *name) { } > > +static inline int ptdump_check_wx_init(void) { return 0; } > > #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 1f2eae3e988b..73cddc12c3c2 100644 > > --- a/arch/arm64/mm/ptdump_debugfs.c > > +++ b/arch/arm64/mm/ptdump_debugfs.c > > @@ -16,3 +16,21 @@ 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"); > > + > > +int ptdump_check_wx_init(void) > > +{ > > + return debugfs_create_file("check_wx_pages", 0200, NULL, > > + NULL, &check_wx_fops) ? 0 : -ENOMEM; > > +} > > -- > > 2.20.1 > > -- Kees Cook