Commit 884d7e2b authored by Chen Zhongjin's avatar Chen Zhongjin
Browse files

x86: profiling: Check prof_buffer in profile_tick() 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9T4EM



--------------------------------

KASAN reported a UAF problem in profile_tick():

  BUG: KASAN: use-after-free in profile_tick+0x5c/0x80
  Read of size 8 at addr ffff888100928aa0 by task bash/1108

  CPU: 2 PID: 1108 Comm: bash Not tainted 5.10.0+ #72
  Call Trace:
   <IRQ>
   dump_stack+0x93/0xc5
   print_address_description.constprop.0+0x1c/0x3c0
   kasan_report.cold+0x37/0x74
   check_memory_region+0x161/0x1c0
   profile_tick+0x5c/0x80
   tick_sched_timer+0xcd/0x100
   __hrtimer_run_queues+0x23e/0x480
   hrtimer_interrupt+0x1c2/0x440
   asm_call_irq_on_stack+0xf/0x20
   </IRQ>
  ...

It is beacause in profiling_store(), profile_init() is possible to fail
and free prof_cpu_mask. However prof_cpu_mask is not set to NULL and
cpumask_available(prof_cpu_mask) will return true in profile_tick().
Then cpumask_test_cpu() will dereference prof_cpu_mask and trigger the
KASAN warning.

There is no interface to disable profile_tick() even though profile_init
has been already failed. And when CONFIG_CPUMASK_OFFSTACK=n, cpumask_var_t
is an array pointer which can not be set to NULL. So prof_cpu_mask can be
a freed pointner or uncleaned array here, and cpumask_available() can't
promise it is safe to use it.

To fix this, add check for prof_buffer in profile_tick() before check
cpumask_available(prof_cpu_mask). Because prof_cpu_mask is available only
after prof_buffer is allocated successfully.

Fixes: c309b917 ("cpumask: convert kernel/profile.c")
Signed-off-by: default avatarChen Zhongjin <chenzhongjin@huawei.com>
parent 43993247

kernel/profile.c

+1 −1
Original line number Diff line number Diff line
@@ -411,7 +411,7 @@ void profile_tick(int type) 
{

	struct pt_regs *regs = get_irq_regs();



	if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&

	if (!user_mode(regs) && prof_buffer && cpumask_available(prof_cpu_mask) &&

	    cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))

		profile_hit(type, (void *)profile_pc(regs));

}