From: Yee Lee yee.lee@mediatek.com
[ Upstream commit 528a4ab45300fa6283556d9b48e26b45a8aa15c4 ]
Since scs allocation is moved to vmalloc region, the shadow stack is protected by kasan_posion_vmalloc. However, the vfree_atomic operation needs to access its context for scs_free process and causes kasan error as the dump info below.
This patch Adds kasan_unpoison_vmalloc() before vfree_atomic, which aligns to the prior flow as using kmem_cache. The vmalloc region will go back posioned in the following vumap() operations.
================================================================== BUG: KASAN: vmalloc-out-of-bounds in llist_add_batch+0x60/0xd4 Write of size 8 at addr ffff8000100b9000 by task kthreadd/2
CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.15.0-rc2-11681-g92477dd1faa6-dirty #1 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x43c show_stack+0x1c/0x2c dump_stack_lvl+0x68/0x84 print_address_description+0x80/0x394 kasan_report+0x180/0x1dc __asan_report_store8_noabort+0x48/0x58 llist_add_batch+0x60/0xd4 vfree_atomic+0x60/0xe0 scs_free+0x1dc/0x1fc scs_release+0xa4/0xd4 free_task+0x30/0xe4 __put_task_struct+0x1ec/0x2e0 delayed_put_task_struct+0x5c/0xa0 rcu_do_batch+0x62c/0x8a0 rcu_core+0x60c/0xc14 rcu_core_si+0x14/0x24 __do_softirq+0x19c/0x68c irq_exit+0x118/0x2dc handle_domain_irq+0xcc/0x134 gic_handle_irq+0x7c/0x1bc call_on_irq_stack+0x40/0x70 do_interrupt_handler+0x78/0x9c el1_interrupt+0x34/0x60 el1h_64_irq_handler+0x1c/0x2c el1h_64_irq+0x78/0x7c _raw_spin_unlock_irqrestore+0x40/0xcc sched_fork+0x4f0/0xb00 copy_process+0xacc/0x3648 kernel_clone+0x168/0x534 kernel_thread+0x13c/0x1b0 kthreadd+0x2bc/0x400 ret_from_fork+0x10/0x20
Memory state around the buggy address: ffff8000100b8f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffff8000100b8f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffff8000100b9000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^ ffff8000100b9080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffff8000100b9100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ==================================================================
Suggested-by: Kuan-Ying Lee kuan-ying.lee@mediatek.com Acked-by: Will Deacon will@kernel.org Tested-by: Will Deacon will@kernel.org Reviewed-by: Sami Tolvanen samitolvanen@google.com Signed-off-by: Yee Lee yee.lee@mediatek.com Fixes: a2abe7cbd8fe ("scs: switch to vmapped shadow stacks") Link: https://lore.kernel.org/r/20210930081619.30091-1-yee.lee@mediatek.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/scs.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/scs.c b/kernel/scs.c index e2a71fc82fa06..579841be88646 100644 --- a/kernel/scs.c +++ b/kernel/scs.c @@ -78,6 +78,7 @@ void scs_free(void *s) if (this_cpu_cmpxchg(scs_cache[i], 0, s) == NULL) return;
+ kasan_unpoison_vmalloc(s, SCS_SIZE); vfree_atomic(s); }