Messages in this thread Patch in this message | | | From | Chen Zhongjin <> | Subject | [PATCH] x86: profiling: Set prof_cpu_mask to NULL after free | Date | Fri, 24 Feb 2023 16:49:45 +0800 |
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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. So just set prof_cpu_mask to NULL when free it. Then accessing to prof_cpu_mask can be rejected by prof_buffer or cpumask_available().
Fixes: c309b917cab5 ("cpumask: convert kernel/profile.c") Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com> --- kernel/profile.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/profile.c b/kernel/profile.c index 8a77769bc4b4..d60f9634fb2a 100644 --- a/kernel/profile.c +++ b/kernel/profile.c @@ -133,6 +133,7 @@ int __ref profile_init(void) return 0; free_cpumask_var(prof_cpu_mask); + prof_cpu_mask = NULL; return -ENOMEM; } @@ -334,7 +335,7 @@ 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)); } -- 2.17.1
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