| Message ID | 20161020062458.14014-1-takahiro.akashi@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > The current "rodata=off" parameter disables read-only kernel mappings > under CONFIG_DEBUG_RODATA: > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter > to disable read-only kernel mappings") > > This patch is a logical extension to module mappings ie. read-only mappings > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX > (mainly for debug use). Please note, however, that it only affects RO/RW > permissions, keeping NX set. > > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. > > Suggested-by: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> > Cc: Rusty Russell <rusty@rustcorp.com.au> > --- > v1: > * remove RFC's "module_ronx=" and merge it with "rodata=" > * always keep NX set if CONFIG_SET_MODULE_RONX > > include/linux/init.h | 3 ++- > init/main.c | 2 +- > kernel/module.c | 21 ++++++++++++++++++--- > 3 files changed, 21 insertions(+), 5 deletions(-) > > diff --git a/include/linux/init.h b/include/linux/init.h > index e30104c..20aa2eb 100644 > --- a/include/linux/init.h > +++ b/include/linux/init.h > @@ -126,7 +126,8 @@ void prepare_namespace(void); > void __init load_default_modules(void); > int __init init_rootfs(void); > > -#ifdef CONFIG_DEBUG_RODATA > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) > +extern bool rodata_enabled; > void mark_rodata_ro(void); > #endif > > diff --git a/init/main.c b/init/main.c > index 2858be7..92db2f3 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) > static noinline void __init kernel_init_freeable(void); > > #ifdef CONFIG_DEBUG_RODATA > -static bool rodata_enabled = true; > +bool rodata_enabled = true; Is there a mismatch here between the extern ifdef and the bool ifdef? I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? Also, can you mark this as __ro_after_init, since nothing changes it after the kernel command line is parsed? Otherwise, this looks fine to me. -Kees
On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: > On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro > <takahiro.akashi@linaro.org> wrote: > > The current "rodata=off" parameter disables read-only kernel mappings > > under CONFIG_DEBUG_RODATA: > > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter > > to disable read-only kernel mappings") > > > > This patch is a logical extension to module mappings ie. read-only mappings > > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX > > (mainly for debug use). Please note, however, that it only affects RO/RW > > permissions, keeping NX set. > > > > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory > > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. > > > > Suggested-by: Mark Rutland <mark.rutland@arm.com> > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> > > Cc: Rusty Russell <rusty@rustcorp.com.au> > > --- > > v1: > > * remove RFC's "module_ronx=" and merge it with "rodata=" > > * always keep NX set if CONFIG_SET_MODULE_RONX > > > > include/linux/init.h | 3 ++- > > init/main.c | 2 +- > > kernel/module.c | 21 ++++++++++++++++++--- > > 3 files changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/init.h b/include/linux/init.h > > index e30104c..20aa2eb 100644 > > --- a/include/linux/init.h > > +++ b/include/linux/init.h > > @@ -126,7 +126,8 @@ void prepare_namespace(void); > > void __init load_default_modules(void); > > int __init init_rootfs(void); > > > > -#ifdef CONFIG_DEBUG_RODATA > > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) > > +extern bool rodata_enabled; > > void mark_rodata_ro(void); > > #endif > > > > diff --git a/init/main.c b/init/main.c > > index 2858be7..92db2f3 100644 > > --- a/init/main.c > > +++ b/init/main.c > > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) > > static noinline void __init kernel_init_freeable(void); > > > > #ifdef CONFIG_DEBUG_RODATA > > -static bool rodata_enabled = true; > > +bool rodata_enabled = true; > > Is there a mismatch here between the extern ifdef and the bool ifdef? > I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? Yes. > Also, can you mark this as __ro_after_init, since nothing changes it > after the kernel command line is parsed? Yes, yes. Thanks, -Takahiro AKASHI > Otherwise, this looks fine to me. > > -Kees > > > -- > Kees Cook > Nexus Security
AKASHI Takahiro <takahiro.akashi@linaro.org> writes: > On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: >> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro >> <takahiro.akashi@linaro.org> wrote: >> > The current "rodata=off" parameter disables read-only kernel mappings >> > under CONFIG_DEBUG_RODATA: >> > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter >> > to disable read-only kernel mappings") >> > >> > This patch is a logical extension to module mappings ie. read-only mappings >> > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX >> > (mainly for debug use). Please note, however, that it only affects RO/RW >> > permissions, keeping NX set. This patch looks good (except the minor issues noted by Kees); please CC the followup version to Jessica as new module maintainer. Thanks! Rusty. >> > >> > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory >> > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. >> > >> > Suggested-by: Mark Rutland <mark.rutland@arm.com> >> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> >> > Cc: Rusty Russell <rusty@rustcorp.com.au> >> > --- >> > v1: >> > * remove RFC's "module_ronx=" and merge it with "rodata=" >> > * always keep NX set if CONFIG_SET_MODULE_RONX >> > >> > include/linux/init.h | 3 ++- >> > init/main.c | 2 +- >> > kernel/module.c | 21 ++++++++++++++++++--- >> > 3 files changed, 21 insertions(+), 5 deletions(-) >> > >> > diff --git a/include/linux/init.h b/include/linux/init.h >> > index e30104c..20aa2eb 100644 >> > --- a/include/linux/init.h >> > +++ b/include/linux/init.h >> > @@ -126,7 +126,8 @@ void prepare_namespace(void); >> > void __init load_default_modules(void); >> > int __init init_rootfs(void); >> > >> > -#ifdef CONFIG_DEBUG_RODATA >> > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) >> > +extern bool rodata_enabled; >> > void mark_rodata_ro(void); >> > #endif >> > >> > diff --git a/init/main.c b/init/main.c >> > index 2858be7..92db2f3 100644 >> > --- a/init/main.c >> > +++ b/init/main.c >> > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) >> > static noinline void __init kernel_init_freeable(void); >> > >> > #ifdef CONFIG_DEBUG_RODATA >> > -static bool rodata_enabled = true; >> > +bool rodata_enabled = true; >> >> Is there a mismatch here between the extern ifdef and the bool ifdef? >> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? > > Yes. > >> Also, can you mark this as __ro_after_init, since nothing changes it >> after the kernel command line is parsed? > > Yes, yes. > > Thanks, > -Takahiro AKASHI > >> Otherwise, this looks fine to me. >> >> -Kees >> >> >> -- >> Kees Cook >> Nexus Security
Rusty, Jessica On Wed, Oct 26, 2016 at 10:43:32AM +1030, Rusty Russell wrote: > AKASHI Takahiro <takahiro.akashi@linaro.org> writes: > > On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: > >> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro > >> <takahiro.akashi@linaro.org> wrote: > >> > The current "rodata=off" parameter disables read-only kernel mappings > >> > under CONFIG_DEBUG_RODATA: > >> > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter > >> > to disable read-only kernel mappings") > >> > > >> > This patch is a logical extension to module mappings ie. read-only mappings > >> > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX > >> > (mainly for debug use). Please note, however, that it only affects RO/RW > >> > permissions, keeping NX set. > > This patch looks good (except the minor issues noted by Kees); please CC > the followup version to Jessica as new module maintainer. I think that the new version (v2)[1] addresses Kees' comments already. [1] http://lkml.iu.edu//hypermail/linux/kernel/1610.2/04163.html Thanks, -Takahiro AKASHI > Thanks! > Rusty. > > >> > > >> > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory > >> > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. > >> > > >> > Suggested-by: Mark Rutland <mark.rutland@arm.com> > >> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> > >> > Cc: Rusty Russell <rusty@rustcorp.com.au> > >> > --- > >> > v1: > >> > * remove RFC's "module_ronx=" and merge it with "rodata=" > >> > * always keep NX set if CONFIG_SET_MODULE_RONX > >> > > >> > include/linux/init.h | 3 ++- > >> > init/main.c | 2 +- > >> > kernel/module.c | 21 ++++++++++++++++++--- > >> > 3 files changed, 21 insertions(+), 5 deletions(-) > >> > > >> > diff --git a/include/linux/init.h b/include/linux/init.h > >> > index e30104c..20aa2eb 100644 > >> > --- a/include/linux/init.h > >> > +++ b/include/linux/init.h > >> > @@ -126,7 +126,8 @@ void prepare_namespace(void); > >> > void __init load_default_modules(void); > >> > int __init init_rootfs(void); > >> > > >> > -#ifdef CONFIG_DEBUG_RODATA > >> > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) > >> > +extern bool rodata_enabled; > >> > void mark_rodata_ro(void); > >> > #endif > >> > > >> > diff --git a/init/main.c b/init/main.c > >> > index 2858be7..92db2f3 100644 > >> > --- a/init/main.c > >> > +++ b/init/main.c > >> > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) > >> > static noinline void __init kernel_init_freeable(void); > >> > > >> > #ifdef CONFIG_DEBUG_RODATA > >> > -static bool rodata_enabled = true; > >> > +bool rodata_enabled = true; > >> > >> Is there a mismatch here between the extern ifdef and the bool ifdef? > >> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? > > > > Yes. > > > >> Also, can you mark this as __ro_after_init, since nothing changes it > >> after the kernel command line is parsed? > > > > Yes, yes. > > > > Thanks, > > -Takahiro AKASHI > > > >> Otherwise, this looks fine to me. > >> > >> -Kees > >> > >> > >> -- > >> Kees Cook > >> Nexus Security
diff --git a/include/linux/init.h b/include/linux/init.h index e30104c..20aa2eb 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -126,7 +126,8 @@ void prepare_namespace(void); void __init load_default_modules(void); int __init init_rootfs(void); -#ifdef CONFIG_DEBUG_RODATA +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) +extern bool rodata_enabled; void mark_rodata_ro(void); #endif diff --git a/init/main.c b/init/main.c index 2858be7..92db2f3 100644 --- a/init/main.c +++ b/init/main.c @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) static noinline void __init kernel_init_freeable(void); #ifdef CONFIG_DEBUG_RODATA -static bool rodata_enabled = true; +bool rodata_enabled = true; static int __init set_debug_rodata(char *str) { return strtobool(str, &rodata_enabled); diff --git a/kernel/module.c b/kernel/module.c index f57dd63..34d1880 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1910,6 +1910,9 @@ static void frob_writable_data(const struct module_layout *layout, /* livepatching wants to disable read-only so it can frob module. */ void module_disable_ro(const struct module *mod) { + if (!rodata_enabled) + return; + frob_text(&mod->core_layout, set_memory_rw); frob_rodata(&mod->core_layout, set_memory_rw); frob_ro_after_init(&mod->core_layout, set_memory_rw); @@ -1919,6 +1922,9 @@ void module_disable_ro(const struct module *mod) void module_enable_ro(const struct module *mod, bool after_init) { + if (!rodata_enabled) + return; + frob_text(&mod->core_layout, set_memory_ro); frob_rodata(&mod->core_layout, set_memory_ro); frob_text(&mod->init_layout, set_memory_ro); @@ -1951,6 +1957,9 @@ void set_all_modules_text_rw(void) { struct module *mod; + if (!rodata_enabled) + return; + mutex_lock(&module_mutex); list_for_each_entry_rcu(mod, &modules, list) { if (mod->state == MODULE_STATE_UNFORMED) @@ -1967,6 +1976,9 @@ void set_all_modules_text_ro(void) { struct module *mod; + if (!rodata_enabled) + return; + mutex_lock(&module_mutex); list_for_each_entry_rcu(mod, &modules, list) { if (mod->state == MODULE_STATE_UNFORMED) @@ -1980,10 +1992,13 @@ void set_all_modules_text_ro(void) static void disable_ro_nx(const struct module_layout *layout) { - frob_text(layout, set_memory_rw); - frob_rodata(layout, set_memory_rw); + if (rodata_enabled) { + frob_text(layout, set_memory_rw); + frob_rodata(layout, set_memory_rw); + } frob_rodata(layout, set_memory_x); - frob_ro_after_init(layout, set_memory_rw); + if (rodata_enabled) + frob_ro_after_init(layout, set_memory_rw); frob_ro_after_init(layout, set_memory_x); frob_writable_data(layout, set_memory_x); }
The current "rodata=off" parameter disables read-only kernel mappings under CONFIG_DEBUG_RODATA: commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings") This patch is a logical extension to module mappings ie. read-only mappings at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX (mainly for debug use). Please note, however, that it only affects RO/RW permissions, keeping NX set. This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. Suggested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Cc: Rusty Russell <rusty@rustcorp.com.au> --- v1: * remove RFC's "module_ronx=" and merge it with "rodata=" * always keep NX set if CONFIG_SET_MODULE_RONX include/linux/init.h | 3 ++- init/main.c | 2 +- kernel/module.c | 21 ++++++++++++++++++--- 3 files changed, 21 insertions(+), 5 deletions(-)