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

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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: c309b917cab5 ("cpumask: convert kernel/profile.c") Signed-off-by: Chen Zhongjin chenzhongjin@huawei.com --- kernel/profile.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/profile.c b/kernel/profile.c index 0db1122855c0d..4134c788d3458 100644 --- a/kernel/profile.c +++ b/kernel/profile.c @@ -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)); }