diff options
| author | Benjamin Gray <bgray@linux.ibm.com> | 2024-04-17 21:23:19 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2024-05-03 20:46:51 +1000 |
| commit | bbd99922d0f4518518282217159666c679c6a0d1 (patch) | |
| tree | 6c2d20d8594157030d86f67582c38370560ccf0b | |
| parent | 75171f06c4507c3b6b5a69d793879fb20d108bb1 (diff) | |
powerpc/dexcr: Reset DEXCR value across exec
Inheriting the DEXCR across exec can have security and usability
concerns. If a program is compiled with hash instructions it generally
expects to run with NPHIE enabled. But if the parent process disables
NPHIE then if it's not careful it will be disabled for any children too
and the protection offered by hash checks is basically worthless.
This patch introduces a per-process reset value that new execs in a
particular process tree are initialized with. This enables fine grained
control over what DEXCR value child processes run with by default.
For example, containers running legacy binaries that expect hash
instructions to act as NOPs could configure the reset value of the
container root to control the default reset value for all members of
the container.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
[mpe: Add missing SPDX tag on dexcr.c]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240417112325.728010-4-bgray@linux.ibm.com
| -rw-r--r-- | arch/powerpc/include/asm/processor.h | 2 | ||||
| -rw-r--r-- | arch/powerpc/kernel/Makefile | 1 | ||||
| -rw-r--r-- | arch/powerpc/kernel/dexcr.c | 23 | ||||
| -rw-r--r-- | arch/powerpc/kernel/process.c | 7 |
4 files changed, 32 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index 882e31296ea6..aad85a24134a 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -261,7 +261,7 @@ struct thread_struct { unsigned long sier3; unsigned long hashkeyr; unsigned long dexcr; - + unsigned long dexcr_onexec; /* Reset value to load on exec */ #endif }; diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index d3282fbea4f2..1d183b077948 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -87,6 +87,7 @@ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o obj-$(CONFIG_PPC_DAWR) += dawr.o obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_ppc970.o cpu_setup_pa6t.o obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o +obj-$(CONFIG_PPC_BOOK3S_64) += dexcr.o obj-$(CONFIG_PPC_BOOK3S_64) += mce.o mce_power.o obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_64e.o obj-$(CONFIG_PPC_BARRIER_NOSPEC) += security.o diff --git a/arch/powerpc/kernel/dexcr.c b/arch/powerpc/kernel/dexcr.c new file mode 100644 index 000000000000..d5cd77421088 --- /dev/null +++ b/arch/powerpc/kernel/dexcr.c @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +#include <linux/capability.h> +#include <linux/cpu.h> +#include <linux/init.h> +#include <linux/prctl.h> +#include <linux/sched.h> + +#include <asm/cpu_has_feature.h> +#include <asm/cputable.h> +#include <asm/processor.h> +#include <asm/reg.h> + +static int __init init_task_dexcr(void) +{ + if (!early_cpu_has_feature(CPU_FTR_ARCH_31)) + return 0; + + current->thread.dexcr_onexec = mfspr(SPRN_DEXCR); + + return 0; +} +early_initcall(init_task_dexcr) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index d482c3fd81d7..8ab779a3bdde 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1641,6 +1641,13 @@ void arch_setup_new_exec(void) current->thread.regs->amr = default_amr; current->thread.regs->iamr = default_iamr; #endif + +#ifdef CONFIG_PPC_BOOK3S_64 + if (cpu_has_feature(CPU_FTR_ARCH_31)) { + current->thread.dexcr = current->thread.dexcr_onexec; + mtspr(SPRN_DEXCR, current->thread.dexcr); + } +#endif /* CONFIG_PPC_BOOK3S_64 */ } #ifdef CONFIG_PPC64 |