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mm/mmap.c: fix a data race of mm->total_vm

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The variable mm->total_vm could be accessed concurrently during mmaping
and system accounting as noticed by KCSAN,

  BUG: KCSAN: data-race in __acct_update_integrals / mmap_region

  read-write to 0xffffa40267bd14c8 of 8 bytes by task 15609 on cpu 3:
   mmap_region+0x6dc/0x1400
   do_mmap+0x794/0xca0
   vm_mmap_pgoff+0xdf/0x150
   ksys_mmap_pgoff+0xe1/0x380
   do_syscall_64+0x37/0x50
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  read to 0xffffa40267bd14c8 of 8 bytes by interrupt on cpu 2:
   __acct_update_integrals+0x187/0x1d0
   acct_account_cputime+0x3c/0x40
   update_process_times+0x5c/0x150
   tick_sched_timer+0x184/0x210
   __run_hrtimer+0x119/0x3b0
   hrtimer_interrupt+0x350/0xaa0
   __sysvec_apic_timer_interrupt+0x7b/0x220
   asm_call_irq_on_stack+0x12/0x20
   sysvec_apic_timer_interrupt+0x4d/0x80
   asm_sysvec_apic_timer_interrupt+0x12/0x20
   smp_call_function_single+0x192/0x2b0
   perf_install_in_context+0x29b/0x4a0
   __se_sys_perf_event_open+0x1a98/0x2550
   __x64_sys_perf_event_open+0x63/0x70
   do_syscall_64+0x37/0x50
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  Reported by Kernel Concurrency Sanitizer on:
  CPU: 2 PID: 15610 Comm: syz-executor.3 Not tainted 5.10.0+ #2
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
  Ubuntu-1.8.2-1ubuntu1 04/01/2014

In vm_stat_account which called by mmap_region, increase total_vm, and
__acct_update_integrals may read total_vm at the same time.  This will
cause a data race which lead to undefined behaviour.  To avoid potential
bad read/write, volatile property and barrier are both used to avoid
undefined behaviour.

Link: https://lkml.kernel.org/r/20210913105550.1569419-1-liupeng256@huawei.com
Signed-off-by: Peng Liu <liupeng256@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peng Liu 2021-11-05 13:38:12 -07:00 committed by Linus Torvalds
parent a4ebf1b6ca
commit 7866076b92
2 changed files with 2 additions and 2 deletions
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2
kernel/tsacct.c
View File

@ -137,7 +137,7 @@ static void __acct_update_integrals(struct task_struct *tsk,
* the rest of the math is done in xacct_add_tsk.
*/
tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm) >> 10;
tsk->acct_vm_mem1 += delta * tsk->mm->total_vm >> 10;
tsk->acct_vm_mem1 += delta * READ_ONCE(tsk->mm->total_vm) >> 10;
}
/**

2
mm/mmap.c
View File

@ -3332,7 +3332,7 @@ bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
{
mm->total_vm += npages;
WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages);
if (is_exec_mapping(flags))
mm->exec_vm += npages;