Some functions are called from handwritten assembly, and therefore don't
have their arguments' metadata fully set up by the instrumentation code.
Mark them with __no_sanitize_memory to avoid false positives from
spreading further.
Certain functions perform task switching, so that the value of |current|
is different as they proceed. Because KMSAN state pointer is only read
once at the beginning of the function, touching it after |current| has
changed may be dangerous.
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
To: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
---
v3:
- removed TODOs from comments
Change-Id: I684d23dac5a22eb0a4cea71993cb934302b17cea
---
arch/x86/entry/common.c | 1 +
arch/x86/include/asm/irq_regs.h | 1 +
arch/x86/include/asm/syscall_wrapper.h | 1 +
arch/x86/kernel/apic/apic.c | 1 +
arch/x86/kernel/dumpstack_64.c | 1 +
arch/x86/kernel/process_64.c | 5 +++++
arch/x86/kernel/traps.c | 12 ++++++++++--
arch/x86/kernel/uprobes.c | 7 ++++++-
kernel/profile.c | 1 +
kernel/sched/core.c | 6 ++++++
10 files changed, 33 insertions(+), 3 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 3f8e22615812..0dd5b2acb355 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -275,6 +275,7 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs)
}
#ifdef CONFIG_X86_64
+__no_sanitize_memory
__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
{
struct thread_info *ti;
diff --git a/arch/x86/include/asm/irq_regs.h b/arch/x86/include/asm/irq_regs.h
index 187ce59aea28..d65a00bd6f02 100644
--- a/arch/x86/include/asm/irq_regs.h
+++ b/arch/x86/include/asm/irq_regs.h
@@ -14,6 +14,7 @@
DECLARE_PER_CPU(struct pt_regs *, irq_regs);
+__no_sanitize_memory
static inline struct pt_regs *get_irq_regs(void)
{
return __this_cpu_read(irq_regs);
diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h
index e046a405743d..43910ce1b53b 100644
--- a/arch/x86/include/asm/syscall_wrapper.h
+++ b/arch/x86/include/asm/syscall_wrapper.h
@@ -159,6 +159,7 @@
ALLOW_ERROR_INJECTION(__x64_sys##name, ERRNO); \
static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+ __no_sanitize_memory \
asmlinkage long __x64_sys##name(const struct pt_regs *regs) \
{ \
return __se_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 9e2dd2b296cd..7b24bda22c38 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1118,6 +1118,7 @@ static void local_apic_timer_interrupt(void)
* [ if a single-CPU system runs an SMP kernel then we call the local
* interrupt as well. Thus we cannot inline the local irq ... ]
*/
+__no_sanitize_memory /* |regs| may be uninitialized */
__visible void __irq_entry smp_apic_timer_interrupt(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 753b8cfe8b8a..ba883d282a43 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -143,6 +143,7 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
return true;
}
+__no_sanitize_memory
int get_stack_info(unsigned long *stack, struct task_struct *task,
struct stack_info *info, unsigned long *visit_mask)
{
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index af64519b2695..70e33150a83a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -500,6 +500,11 @@ void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp)
* Kprobes not supported here. Set the probe on schedule instead.
* Function graph tracer not supported too.
*/
+/*
+ * Avoid touching KMSAN state or reporting anything here, as __switch_to() does
+ * weird things with tasks.
+ */
+__no_sanitize_memory
__visible __notrace_funcgraph struct task_struct *
__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
{
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 4bb0f8447112..a94282d1f60b 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -618,7 +618,10 @@ NOKPROBE_SYMBOL(do_int3);
* Help handler running on a per-cpu (IST or entry trampoline) stack
* to switch to the normal thread stack if the interrupted code was in
* user mode. The actual stack switch is done in entry_64.S
+ *
+ * This function switches the registers - don't instrument it with KMSAN!
*/
+__no_sanitize_memory
asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs)
{
struct pt_regs *regs = (struct pt_regs *)this_cpu_read(cpu_current_top_of_stack) - 1;
@@ -634,6 +637,11 @@ struct bad_iret_stack {
};
asmlinkage __visible notrace
+/*
+ * Dark magic happening here, let's not instrument this function.
+ * Also avoid copying any metadata by using raw __memmove().
+ */
+__no_sanitize_memory
struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
{
/*
@@ -648,10 +656,10 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
(struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
/* Copy the IRET target to the new stack. */
- memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
+ __memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
/* Copy the remainder of the stack from the current stack. */
- memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
+ __memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
BUG_ON(!user_mode(&new_stack->regs));
return new_stack;
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 8cd745ef8c7b..bcd4bf5a909f 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -8,6 +8,7 @@
* Jim Keniston
*/
#include <linux/kernel.h>
+#include <linux/kmsan-checks.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
@@ -997,9 +998,13 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
{
struct die_args *args = data;
- struct pt_regs *regs = args->regs;
+ struct pt_regs *regs;
int ret = NOTIFY_DONE;
+ kmsan_unpoison_shadow(args, sizeof(*args));
+ regs = args->regs;
+ if (regs)
+ kmsan_unpoison_shadow(regs, sizeof(*regs));
/* We are only interested in userspace traps */
if (regs && !user_mode(regs))
return NOTIFY_DONE;
diff --git a/kernel/profile.c b/kernel/profile.c
index af7c94bf5fa1..835a5b66d1a4 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -399,6 +399,7 @@ void profile_hits(int type, void *__pc, unsigned int nr_hits)
}
EXPORT_SYMBOL_GPL(profile_hits);
+__no_sanitize_memory
void profile_tick(int type)
{
struct pt_regs *regs = get_irq_regs();
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index dd05a378631a..674d36fe9d44 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -475,6 +475,7 @@ void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
put_task_struct(task);
}
+__no_sanitize_memory /* context switching here */
void wake_up_q(struct wake_q_head *head)
{
struct wake_q_node *node = head->first;
@@ -3180,6 +3181,7 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
* past. prev == current is still correct but we need to recalculate this_rq
* because prev may have moved to another CPU.
*/
+__no_sanitize_memory /* |current| changes here */
static struct rq *finish_task_switch(struct task_struct *prev)
__releases(rq->lock)
{
@@ -3986,6 +3988,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
*
* WARNING: must be called with preemption disabled!
*/
+__no_sanitize_memory /* |current| changes here */
static void __sched notrace __schedule(bool preempt)
{
struct task_struct *prev, *next;
@@ -4605,6 +4608,7 @@ int task_prio(const struct task_struct *p)
*
* Return: 1 if the CPU is currently idle. 0 otherwise.
*/
+__no_sanitize_memory /* nothing to report here */
int idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
@@ -6544,6 +6548,7 @@ static struct kmem_cache *task_group_cache __read_mostly;
DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
+__no_sanitize_memory
void __init sched_init(void)
{
unsigned long ptr = 0;
@@ -6716,6 +6721,7 @@ static inline int preempt_count_equals(int preempt_offset)
return (nested == preempt_offset);
}
+__no_sanitize_memory /* expect the arguments to be initialized */
void __might_sleep(const char *file, int line, int preempt_offset)
{
/*
--
2.24.0.432.g9d3f5f5b63-goog
