| Message ID | 20250122171925.25472-3-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Allow default HARDENED_USERCOPY to be set at compile time | expand |
On Wed, Jan 22, 2025 at 05:19:23PM +0000, Mel Gorman wrote: > HARDENED_USERCOPY defaults to on if enabled at compile time. Allow > hardened_usercopy= default to be set at compile time similar to > init_on_alloc= and init_on_free=. The intent is that hardening > options that can be disabled at runtime can set their default at > build time. > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > Documentation/admin-guide/kernel-parameters.txt | 4 +++- > mm/usercopy.c | 3 ++- > security/Kconfig.hardening | 8 ++++++++ > 3 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 3872bc6ec49d..5d759b20540a 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1773,7 +1773,9 @@ > allocation boundaries as a proactive defense > against bounds-checking flaws in the kernel's > copy_to_user()/copy_from_user() interface. > - on Perform hardened usercopy checks (default). > + The default is determined by > + CONFIG_HARDENED_USERCOPY_DEFAULT_ON. > + on Perform hardened usercopy checks. > off Disable hardened usercopy checks. > > hardlockup_all_cpu_backtrace= > diff --git a/mm/usercopy.c b/mm/usercopy.c > index 83c164aba6e0..4cf33305347a 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -255,7 +255,8 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) > } > EXPORT_SYMBOL(__check_object_size); > > -static bool enable_checks __initdata = true; > +static bool enable_checks __initdata = > + IS_ENABLED(CONFIG_HARDENED_USERCOPY_DEFAULT_ON); > > static int __init parse_hardened_usercopy(char *str) > { > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening > index 9088d613d519..adcc260839c7 100644 > --- a/security/Kconfig.hardening > +++ b/security/Kconfig.hardening > @@ -293,6 +293,14 @@ config HARDENED_USERCOPY > or are part of the kernel text. This prevents entire classes > of heap overflow exploits and similar kernel memory exposures. > > +config HARDENED_USERCOPY_DEFAULT_ON > + bool "Harden memory copies by default" > + depends on HARDENED_USERCOPY > + default n This must be "default HARDENED_USERCOPY" or existing distro builds will break. All major distros enable this by default, and I don't want to risk HARDENED_USERCOPY_DEFAULT_ON getting missed and getting globally disabled. > + help > + This has the effect of setting "hardened_usercopy=on" on the kernel > + command line. This can be disabled with "hardened_usercopy=off". > + > endmenu > > menu "Hardening of kernel data structures" -Kees
On Wed, Jan 22, 2025 at 04:57:37PM -0800, Kees Cook wrote: > On Wed, Jan 22, 2025 at 05:19:23PM +0000, Mel Gorman wrote: > > HARDENED_USERCOPY defaults to on if enabled at compile time. Allow > > hardened_usercopy= default to be set at compile time similar to > > init_on_alloc= and init_on_free=. The intent is that hardening > > options that can be disabled at runtime can set their default at > > build time. > > > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > --- > > Documentation/admin-guide/kernel-parameters.txt | 4 +++- > > mm/usercopy.c | 3 ++- > > security/Kconfig.hardening | 8 ++++++++ > > 3 files changed, 13 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 3872bc6ec49d..5d759b20540a 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -1773,7 +1773,9 @@ > > allocation boundaries as a proactive defense > > against bounds-checking flaws in the kernel's > > copy_to_user()/copy_from_user() interface. > > - on Perform hardened usercopy checks (default). > > + The default is determined by > > + CONFIG_HARDENED_USERCOPY_DEFAULT_ON. > > + on Perform hardened usercopy checks. > > off Disable hardened usercopy checks. > > > > hardlockup_all_cpu_backtrace= > > diff --git a/mm/usercopy.c b/mm/usercopy.c > > index 83c164aba6e0..4cf33305347a 100644 > > --- a/mm/usercopy.c > > +++ b/mm/usercopy.c > > @@ -255,7 +255,8 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) > > } > > EXPORT_SYMBOL(__check_object_size); > > > > -static bool enable_checks __initdata = true; > > +static bool enable_checks __initdata = > > + IS_ENABLED(CONFIG_HARDENED_USERCOPY_DEFAULT_ON); > > > > static int __init parse_hardened_usercopy(char *str) > > { > > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening > > index 9088d613d519..adcc260839c7 100644 > > --- a/security/Kconfig.hardening > > +++ b/security/Kconfig.hardening > > @@ -293,6 +293,14 @@ config HARDENED_USERCOPY > > or are part of the kernel text. This prevents entire classes > > of heap overflow exploits and similar kernel memory exposures. > > > > +config HARDENED_USERCOPY_DEFAULT_ON > > + bool "Harden memory copies by default" > > + depends on HARDENED_USERCOPY > > + default n > > This must be "default HARDENED_USERCOPY" or existing distro builds will > break. All major distros enable this by default, and I don't want to > risk HARDENED_USERCOPY_DEFAULT_ON getting missed and getting globally > disabled. > Ok. I dislike that HARDENED_USERCOPY will be inconsistent with INIT_ON* but it's not a hill I'm willing to die on. Will be in v3
... > > +config HARDENED_USERCOPY_DEFAULT_ON > > + bool "Harden memory copies by default" > > + depends on HARDENED_USERCOPY > > + default n > > This must be "default HARDENED_USERCOPY" or existing distro builds will > break. All major distros enable this by default, and I don't want to > risk HARDENED_USERCOPY_DEFAULT_ON getting missed and getting globally > disabled. It'll also cause grief for anyone trying to bisect. Although that is always going to go wrong if it has been disabled. I had 'fun' trying to locate a massive slowdown of a single threaded program that was caused by a side effect of one of the speculative execution mitigations getting enabled because the config parameter got renamed. David
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3872bc6ec49d..5d759b20540a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1773,7 +1773,9 @@ allocation boundaries as a proactive defense against bounds-checking flaws in the kernel's copy_to_user()/copy_from_user() interface. - on Perform hardened usercopy checks (default). + The default is determined by + CONFIG_HARDENED_USERCOPY_DEFAULT_ON. + on Perform hardened usercopy checks. off Disable hardened usercopy checks. hardlockup_all_cpu_backtrace= diff --git a/mm/usercopy.c b/mm/usercopy.c index 83c164aba6e0..4cf33305347a 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -255,7 +255,8 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) } EXPORT_SYMBOL(__check_object_size); -static bool enable_checks __initdata = true; +static bool enable_checks __initdata = + IS_ENABLED(CONFIG_HARDENED_USERCOPY_DEFAULT_ON); static int __init parse_hardened_usercopy(char *str) { diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 9088d613d519..adcc260839c7 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -293,6 +293,14 @@ config HARDENED_USERCOPY or are part of the kernel text. This prevents entire classes of heap overflow exploits and similar kernel memory exposures. +config HARDENED_USERCOPY_DEFAULT_ON + bool "Harden memory copies by default" + depends on HARDENED_USERCOPY + default n + help + This has the effect of setting "hardened_usercopy=on" on the kernel + command line. This can be disabled with "hardened_usercopy=off". + endmenu menu "Hardening of kernel data structures"
HARDENED_USERCOPY defaults to on if enabled at compile time. Allow hardened_usercopy= default to be set at compile time similar to init_on_alloc= and init_on_free=. The intent is that hardening options that can be disabled at runtime can set their default at build time. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> --- Documentation/admin-guide/kernel-parameters.txt | 4 +++- mm/usercopy.c | 3 ++- security/Kconfig.hardening | 8 ++++++++ 3 files changed, 13 insertions(+), 2 deletions(-)