Re: [Devel] [PATCH vz8 v3 1/2] x86, cpuinfo: Fix race on parallel /proc/cpuinfo read

2020-11-03 Thread Kirill Tkhai 
On 03.11.2020 17:36, Andrey Ryabinin wrote:
> If several threads read /proc/cpuinfo some can see in 'flags'
> values from c->x86_capability, before __do_cpuid_fault() called
> and masks applied. Fix this by forming 'flags' on stack first
> and copy them in per_cpu(cpu_flags, cpu) as a last step.
> 
> https://jira.sw.ru/browse/PSBM-121823
> Signed-off-by: Andrey Ryabinin 

Reviewed-by: Kirill Tkhai 

> ---
> 
> Changes since v1:
>  - none
> 
> Changes since v2:
>  - add spinlock, use temporary ve_flags in show_cpuinfo()
>  
>  arch/x86/kernel/cpu/proc.c | 31 ++-
>  1 file changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> index 4fe1577d5e6f..08fd7ff9a55b 100644
> --- a/arch/x86/kernel/cpu/proc.c
> +++ b/arch/x86/kernel/cpu/proc.c
> @@ -65,15 +65,16 @@ struct cpu_flags {
>  };
>  
>  static DEFINE_PER_CPU(struct cpu_flags, cpu_flags);
> +static DEFINE_SPINLOCK(cpu_flags_lock);
>  
>  static void init_cpu_flags(void *dummy)
>  {
>   int cpu = smp_processor_id();
> - struct cpu_flags *flags = _cpu(cpu_flags, cpu);
> + struct cpu_flags flags;
>   struct cpuinfo_x86 *c = _data(cpu);
>   unsigned int eax, ebx, ecx, edx;
>  
> - memcpy(flags->val, c->x86_capability, NCAPINTS * sizeof(u32));
> + memcpy(, c->x86_capability, sizeof(flags));
>  
>   /*
>* Clear feature bits masked using cpuid masking/faulting.
> @@ -81,26 +82,30 @@ static void init_cpu_flags(void *dummy)
>  
>   if (c->cpuid_level >= 0x0001) {
>   __do_cpuid_fault(0x0001, 0, , , , );
> - flags->val[4] &= ecx;
> - flags->val[0] &= edx;
> + flags.val[4] &= ecx;
> + flags.val[0] &= edx;
>   }
>  
>   if (c->cpuid_level >= 0x0007) {
>   __do_cpuid_fault(0x0007, 0, , , , );
> - flags->val[9] &= ebx;
> + flags.val[9] &= ebx;
>   }
>  
>   if ((c->extended_cpuid_level & 0x) == 0x8000 &&
>   c->extended_cpuid_level >= 0x8001) {
>   __do_cpuid_fault(0x8001, 0, , , , );
> - flags->val[6] &= ecx;
> - flags->val[1] &= edx;
> + flags.val[6] &= ecx;
> + flags.val[1] &= edx;
>   }
>  
>   if (c->cpuid_level >= 0x000d) {
>   __do_cpuid_fault(0x000d, 1, , , , );
> - flags->val[10] &= eax;
> + flags.val[10] &= eax;
>   }
> +
> + spin_lock(_flags_lock);
> + memcpy(_cpu(cpu_flags, cpu), , sizeof(flags));
> + spin_unlock(_flags_lock);
>  }
>  
>  static int show_cpuinfo(struct seq_file *m, void *v)
> @@ -108,6 +113,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
>   struct cpuinfo_x86 *c = v;
>   unsigned int cpu;
>   int is_super = ve_is_super(get_exec_env());
> + struct cpu_flags ve_flags;
>   int i;
>  
>   cpu = c->cpu_index;
> @@ -147,12 +153,19 @@ static int show_cpuinfo(struct seq_file *m, void *v)
>   show_cpuinfo_core(m, c, cpu);
>   show_cpuinfo_misc(m, c);
>  
> + if (!is_super) {
> + spin_lock_irq(_flags_lock);
> + memcpy(_flags, _cpu(cpu_flags, cpu), sizeof(ve_flags));
> + spin_unlock_irq(_flags_lock);
> + }
> +
> +
>   seq_puts(m, "flags\t\t:");
>   for (i = 0; i < 32*NCAPINTS; i++)
>   if (x86_cap_flags[i] != NULL &&
>   ((is_super && cpu_has(c, i)) ||
>(!is_super && test_bit(i, (unsigned long *)
> - _cpu(cpu_flags, 
> cpu)
> + _flags
>   seq_printf(m, " %s", x86_cap_flags[i]);
>  
>   seq_puts(m, "\nbugs\t\t:");
> 

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[Devel] [PATCH vz8 v3 1/2] x86, cpuinfo: Fix race on parallel /proc/cpuinfo read

2020-11-03 Thread Andrey Ryabinin 
If several threads read /proc/cpuinfo some can see in 'flags'
values from c->x86_capability, before __do_cpuid_fault() called
and masks applied. Fix this by forming 'flags' on stack first
and copy them in per_cpu(cpu_flags, cpu) as a last step.

https://jira.sw.ru/browse/PSBM-121823
Signed-off-by: Andrey Ryabinin 
---

Changes since v1:
 - none

Changes since v2:
 - add spinlock, use temporary ve_flags in show_cpuinfo()
 
 arch/x86/kernel/cpu/proc.c | 31 ++-
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 4fe1577d5e6f..08fd7ff9a55b 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -65,15 +65,16 @@ struct cpu_flags {
 };
 
 static DEFINE_PER_CPU(struct cpu_flags, cpu_flags);
+static DEFINE_SPINLOCK(cpu_flags_lock);
 
 static void init_cpu_flags(void *dummy)
 {
int cpu = smp_processor_id();
-   struct cpu_flags *flags = _cpu(cpu_flags, cpu);
+   struct cpu_flags flags;
struct cpuinfo_x86 *c = _data(cpu);
unsigned int eax, ebx, ecx, edx;
 
-   memcpy(flags->val, c->x86_capability, NCAPINTS * sizeof(u32));
+   memcpy(, c->x86_capability, sizeof(flags));
 
/*
 * Clear feature bits masked using cpuid masking/faulting.
@@ -81,26 +82,30 @@ static void init_cpu_flags(void *dummy)
 
if (c->cpuid_level >= 0x0001) {
__do_cpuid_fault(0x0001, 0, , , , );
-   flags->val[4] &= ecx;
-   flags->val[0] &= edx;
+   flags.val[4] &= ecx;
+   flags.val[0] &= edx;
}
 
if (c->cpuid_level >= 0x0007) {
__do_cpuid_fault(0x0007, 0, , , , );
-   flags->val[9] &= ebx;
+   flags.val[9] &= ebx;
}
 
if ((c->extended_cpuid_level & 0x) == 0x8000 &&
c->extended_cpuid_level >= 0x8001) {
__do_cpuid_fault(0x8001, 0, , , , );
-   flags->val[6] &= ecx;
-   flags->val[1] &= edx;
+   flags.val[6] &= ecx;
+   flags.val[1] &= edx;
}
 
if (c->cpuid_level >= 0x000d) {
__do_cpuid_fault(0x000d, 1, , , , );
-   flags->val[10] &= eax;
+   flags.val[10] &= eax;
}
+
+   spin_lock(_flags_lock);
+   memcpy(_cpu(cpu_flags, cpu), , sizeof(flags));
+   spin_unlock(_flags_lock);
 }
 
 static int show_cpuinfo(struct seq_file *m, void *v)
@@ -108,6 +113,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
struct cpuinfo_x86 *c = v;
unsigned int cpu;
int is_super = ve_is_super(get_exec_env());
+   struct cpu_flags ve_flags;
int i;
 
cpu = c->cpu_index;
@@ -147,12 +153,19 @@ static int show_cpuinfo(struct seq_file *m, void *v)
show_cpuinfo_core(m, c, cpu);
show_cpuinfo_misc(m, c);
 
+   if (!is_super) {
+   spin_lock_irq(_flags_lock);
+   memcpy(_flags, _cpu(cpu_flags, cpu), sizeof(ve_flags));
+   spin_unlock_irq(_flags_lock);
+   }
+
+
seq_puts(m, "flags\t\t:");
for (i = 0; i < 32*NCAPINTS; i++)
if (x86_cap_flags[i] != NULL &&
((is_super && cpu_has(c, i)) ||
 (!is_super && test_bit(i, (unsigned long *)
-   _cpu(cpu_flags, 
cpu)
+   _flags
seq_printf(m, " %s", x86_cap_flags[i]);
 
seq_puts(m, "\nbugs\t\t:");
-- 
2.26.2

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