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Date: Thu, 7 Apr 2022 07:39:51 +0000 From: Christophe Leroy <christophe.leroy@...roup.eu> To: Kees Cook <keescook@...omium.org>, Russell Currey <ruscur@...sell.cc>, "jniethe5@...il.com" <jniethe5@...il.com> CC: "ajd@...ux.ibm.com" <ajd@...ux.ibm.com>, "npiggin@...il.com" <npiggin@...il.com>, "joel@....id.au" <joel@....id.au>, "dja@...ens.net" <dja@...ens.net>, "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>, "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org> Subject: Re: [PATCH v5 3/8] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Le 06/04/2022 à 20:55, Kees Cook a écrit : > *thread necromancy* > > Is this patch still something folks are working on? It'd be nice to be > able to trigger this check at runtime. The series was taken over by Jordan. v15 of the series was accepted, but that particular patch was dropped in v11 (see https://patchwork.ozlabs.org/project/linuxppc-dev/cover/20210429031602.2606654-1-jniethe5@gmail.com/) The comment was: Some patches were dropped from this revision: powerpc/mm/ptdump: debugfs handler for W+X checks at runtime - Will use Christophe's generic ptdump series Not sure what happened after that. Christophe > > -Kees > > On Wed, Feb 26, 2020 at 05:35:46PM +1100, Russell Currey wrote: >> Very rudimentary, just >> >> echo 1 > [debugfs]/check_wx_pages >> >> and check the kernel log. Useful for testing strict module RWX. >> >> Updated the Kconfig entry to reflect this. >> >> Also fixed a typo. >> >> Signed-off-by: Russell Currey <ruscur@...sell.cc> >> --- >> arch/powerpc/Kconfig.debug | 6 ++++-- >> arch/powerpc/mm/ptdump/ptdump.c | 21 ++++++++++++++++++++- >> 2 files changed, 24 insertions(+), 3 deletions(-) >> >> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug >> index 0b063830eea8..e37960ef68c6 100644 >> --- a/arch/powerpc/Kconfig.debug >> +++ b/arch/powerpc/Kconfig.debug >> @@ -370,7 +370,7 @@ config PPC_PTDUMP >> If you are unsure, say N. >> >> config PPC_DEBUG_WX >> - bool "Warn on W+X mappings at boot" >> + bool "Warn on W+X mappings at boot & enable manual checks at runtime" >> depends on PPC_PTDUMP && STRICT_KERNEL_RWX >> help >> Generate a warning if any W+X mappings are found at boot. >> @@ -384,7 +384,9 @@ config PPC_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 only automatically checks once. >> + >> + Enables the "check_wx_pages" debugfs entry for checking at runtime. >> >> If in doubt, say "Y". >> >> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c >> index 206156255247..a15e19a3b14e 100644 >> --- a/arch/powerpc/mm/ptdump/ptdump.c >> +++ b/arch/powerpc/mm/ptdump/ptdump.c >> @@ -4,7 +4,7 @@ >> * >> * This traverses the kernel pagetables and dumps the >> * information about the used sections of memory to >> - * /sys/kernel/debug/kernel_pagetables. >> + * /sys/kernel/debug/kernel_page_tables. >> * >> * Derived from the arm64 implementation: >> * Copyright (c) 2014, The Linux Foundation, Laura Abbott. >> @@ -413,6 +413,25 @@ void ptdump_check_wx(void) >> else >> pr_info("Checked W+X mappings: passed, no W+X pages found\n"); >> } >> + >> +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"); >> + >> +static int ptdump_check_wx_init(void) >> +{ >> + return debugfs_create_file("check_wx_pages", 0200, NULL, >> + NULL, &check_wx_fops) ? 0 : -ENOMEM; >> +} >> +device_initcall(ptdump_check_wx_init); >> #endif >> >> static int ptdump_init(void) >> -- >> 2.25.1 >> >
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