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powerpc/kasan: Don't instrument non-maskable or raw interrupts 

Disable address sanitization for raw and non-maskable interrupt
handlers, because they can run in real mode, where we cannot access
the shadow memory.  (Note that kasan_arch_is_ready() doesn't test for
real mode, since it is a static branch for speed, and in any case not
all the entry points to the generic KASAN code are protected by
kasan_arch_is_ready guards.)

The changes to interrupt_nmi_enter/exit_prepare() look larger than
they actually are.  The changes are equivalent to adding
!IS_ENABLED(CONFIG_KASAN) to the conditions for calling nmi_enter() or
nmi_exit() in real mode.  That is, the code is equivalent to using the
following condition for calling nmi_enter/exit:

	if (((!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
			!firmware_has_feature(FW_FEATURE_LPAR) ||
			radix_enabled()) &&
		    !IS_ENABLED(CONFIG_KASAN) ||
		(mfmsr() & MSR_DR))

That unwieldy condition has been split into several statements with
comments, for easier reading.

The nmi_ipi_lock functions that call atomic functions (i.e.,
nmi_ipi_lock_start(), nmi_ipi_lock() and nmi_ipi_unlock()), besides
being marked noinstr, now call arch_atomic_* functions instead of
atomic_* functions because with KASAN enabled, the atomic_* functions
are wrappers which explicitly do address sanitization on their
arguments.  Since we are trying to avoid address sanitization, we have
to use the lower-level arch_atomic_* versions.

In hv_nmi_check_nonrecoverable(), the regs_set_unrecoverable() call
has been open-coded so as to avoid having to either trust the inlining
or mark regs_set_unrecoverable() as noinstr.

[paulus@ozlabs.org: combined a few work-in-progress commits of
 Daniel's and wrote the commit message.]

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/YoTFGaKM8Pd46PIK@cleo
This commit is contained in:
Daniel Axtens 2022-05-18 20:06:17 +10:00 committed by Michael Ellerman
parent f08aed5241
commit 5352090a99
5 changed files with 59 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
arch/powerpc/include/asm/interrupt.h
View File

@ -324,22 +324,46 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
}
#endif
/* If data relocations are enabled, it's safe to use nmi_enter() */
if (mfmsr() & MSR_DR) {
nmi_enter();
return;
}
/*
* Do not use nmi_enter() for pseries hash guest taking a real-mode
* But do not use nmi_enter() for pseries hash guest taking a real-mode
* NMI because not everything it touches is within the RMA limit.
*/
if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
!firmware_has_feature(FW_FEATURE_LPAR) ||
radix_enabled() || (mfmsr() & MSR_DR))
nmi_enter();
if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
firmware_has_feature(FW_FEATURE_LPAR) &&
!radix_enabled())
return;
/*
* Likewise, don't use it if we have some form of instrumentation (like
* KASAN shadow) that is not safe to access in real mode (even on radix)
*/
if (IS_ENABLED(CONFIG_KASAN))
return;
/* Otherwise, it should be safe to call it */
nmi_enter();
}
static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct interrupt_nmi_state *state)
{
if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64) ||
!firmware_has_feature(FW_FEATURE_LPAR) ||
radix_enabled() || (mfmsr() & MSR_DR))
if (mfmsr() & MSR_DR) {
// nmi_exit if relocations are on
nmi_exit();
} else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
firmware_has_feature(FW_FEATURE_LPAR) &&
!radix_enabled()) {
// no nmi_exit for a pseries hash guest taking a real mode exception
} else if (IS_ENABLED(CONFIG_KASAN)) {
// no nmi_exit for KASAN in real mode
} else {
nmi_exit();
}
/*
* nmi does not call nap_adjust_return because nmi should not create
@ -407,7 +431,8 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
* Specific handlers may have additional restrictions.
*/
#define DEFINE_INTERRUPT_HANDLER_RAW(func) \
static __always_inline long ____##func(struct pt_regs *regs); \
static __always_inline __no_sanitize_address __no_kcsan long \
____##func(struct pt_regs *regs); \
\
interrupt_handler long func(struct pt_regs *regs) \
{ \
@ -421,7 +446,8 @@ interrupt_handler long func(struct pt_regs *regs) \
} \
NOKPROBE_SYMBOL(func); \
\
static __always_inline long ____##func(struct pt_regs *regs)
static __always_inline __no_sanitize_address __no_kcsan long \
____##func(struct pt_regs *regs)
/**
* DECLARE_INTERRUPT_HANDLER - Declare synchronous interrupt handler function
@ -541,7 +567,8 @@ static __always_inline void ____##func(struct pt_regs *regs)
* body with a pair of curly brackets.
*/
#define DEFINE_INTERRUPT_HANDLER_NMI(func) \
static __always_inline long ____##func(struct pt_regs *regs); \
static __always_inline __no_sanitize_address __no_kcsan long \
____##func(struct pt_regs *regs); \
\
interrupt_handler long func(struct pt_regs *regs) \
{ \
@ -558,7 +585,8 @@ interrupt_handler long func(struct pt_regs *regs) \
} \
NOKPROBE_SYMBOL(func); \
\
static __always_inline long ____##func(struct pt_regs *regs)
static __always_inline __no_sanitize_address __no_kcsan long \
____##func(struct pt_regs *regs)
/* Interrupt handlers */

22
arch/powerpc/kernel/smp.c
View File

@ -411,32 +411,32 @@ static struct cpumask nmi_ipi_pending_mask;
static bool nmi_ipi_busy = false;
static void (*nmi_ipi_function)(struct pt_regs *) = NULL;
static void nmi_ipi_lock_start(unsigned long *flags)
noinstr static void nmi_ipi_lock_start(unsigned long *flags)
{
raw_local_irq_save(*flags);
hard_irq_disable();
while (atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1) {
while (arch_atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1) {
raw_local_irq_restore(*flags);
spin_until_cond(atomic_read(&__nmi_ipi_lock) == 0);
spin_until_cond(arch_atomic_read(&__nmi_ipi_lock) == 0);
raw_local_irq_save(*flags);
hard_irq_disable();
}
}
static void nmi_ipi_lock(void)
noinstr static void nmi_ipi_lock(void)
{
while (atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1)
spin_until_cond(atomic_read(&__nmi_ipi_lock) == 0);
while (arch_atomic_cmpxchg(&__nmi_ipi_lock, 0, 1) == 1)
spin_until_cond(arch_atomic_read(&__nmi_ipi_lock) == 0);
}
static void nmi_ipi_unlock(void)
noinstr static void nmi_ipi_unlock(void)
{
smp_mb();
WARN_ON(atomic_read(&__nmi_ipi_lock) != 1);
atomic_set(&__nmi_ipi_lock, 0);
WARN_ON(arch_atomic_read(&__nmi_ipi_lock) != 1);
arch_atomic_set(&__nmi_ipi_lock, 0);
}
static void nmi_ipi_unlock_end(unsigned long *flags)
noinstr static void nmi_ipi_unlock_end(unsigned long *flags)
{
nmi_ipi_unlock();
raw_local_irq_restore(*flags);
@ -445,7 +445,7 @@ static void nmi_ipi_unlock_end(unsigned long *flags)
/*
* Platform NMI handler calls this to ack
*/
int smp_handle_nmi_ipi(struct pt_regs *regs)
noinstr int smp_handle_nmi_ipi(struct pt_regs *regs)
{
void (*fn)(struct pt_regs *) = NULL;
unsigned long flags;

6
arch/powerpc/kernel/traps.c
View File

@ -393,7 +393,7 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
* Builds that do not support KVM could take this second option to increase
* the recoverability of NMIs.
*/
void hv_nmi_check_nonrecoverable(struct pt_regs *regs)
noinstr void hv_nmi_check_nonrecoverable(struct pt_regs *regs)
{
#ifdef CONFIG_PPC_POWERNV
unsigned long kbase = (unsigned long)_stext;
@ -433,7 +433,9 @@ void hv_nmi_check_nonrecoverable(struct pt_regs *regs)
return;
nonrecoverable:
regs_set_unrecoverable(regs);
regs->msr &= ~MSR_RI;
local_paca->hsrr_valid = 0;
local_paca->srr_valid = 0;
#endif
}
DEFINE_INTERRUPT_HANDLER_NMI(system_reset_exception)

3
arch/powerpc/lib/Makefile
View File

@ -13,6 +13,9 @@ CFLAGS_REMOVE_feature-fixups.o = $(CC_FLAGS_FTRACE)
KASAN_SANITIZE_code-patching.o := n
KASAN_SANITIZE_feature-fixups.o := n
# restart_table.o contains functions called in the NMI interrupt path
# which can be in real mode. Disable KASAN.
KASAN_SANITIZE_restart_table.o := n
ifdef CONFIG_KASAN
CFLAGS_code-patching.o += -DDISABLE_BRANCH_PROFILING

2
arch/powerpc/platforms/powernv/smp.c
View File

@ -345,7 +345,7 @@ static void __init pnv_smp_probe(void)
}
}
static int pnv_system_reset_exception(struct pt_regs *regs)
noinstr static int pnv_system_reset_exception(struct pt_regs *regs)
{
if (smp_handle_nmi_ipi(regs))
return 1;