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 <[email protected]>
---
v1 [https://lore.kernel.org/lkml/[email protected]/T/]
-> v2:
Only check prof_buffer in profile_tick() but not set prof_cpu_mask
to NULL after free_cpumask_var()
---
kernel/profile.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/profile.c b/kernel/profile.c
index 8a77769bc4b4..cca47dc2b1db 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -334,7 +334,7 @@ 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