[PATCH] arm: kasan: clear stale stack poison

[boy . wu]

From: Boy Wu <boy.wu@xxxxxxxxxxxx>

We found below OOB crash:

[   33.452494] ==================================================================
[   33.453513] BUG: KASAN: stack-out-of-bounds in refresh_cpu_vm_stats.constprop.0+0xcc/0x2ec
[   33.454660] Write of size 164 at addr c1d03d30 by task swapper/0/0
[   33.455515]
[   33.455767] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G           O       6.1.25-mainline #1
[   33.456880] Hardware name: Generic DT based system
[   33.457555]  unwind_backtrace from show_stack+0x18/0x1c
[   33.458326]  show_stack from dump_stack_lvl+0x40/0x4c
[   33.459072]  dump_stack_lvl from print_report+0x158/0x4a4
[   33.459863]  print_report from kasan_report+0x9c/0x148
[   33.460616]  kasan_report from kasan_check_range+0x94/0x1a0
[   33.461424]  kasan_check_range from memset+0x20/0x3c
[   33.462157]  memset from refresh_cpu_vm_stats.constprop.0+0xcc/0x2ec
[   33.463064]  refresh_cpu_vm_stats.constprop.0 from tick_nohz_idle_stop_tick+0x180/0x53c
[   33.464181]  tick_nohz_idle_stop_tick from do_idle+0x264/0x354
[   33.465029]  do_idle from cpu_startup_entry+0x20/0x24
[   33.465769]  cpu_startup_entry from rest_init+0xf0/0xf4
[   33.466528]  rest_init from arch_post_acpi_subsys_init+0x0/0x18
[   33.467397]
[   33.467644] The buggy address belongs to stack of task swapper/0/0
[   33.468493]  and is located at offset 112 in frame:
[   33.469172]  refresh_cpu_vm_stats.constprop.0+0x0/0x2ec
[   33.469917]
[   33.470165] This frame has 2 objects:
[   33.470696]  [32, 76) 'global_zone_diff'
[   33.470729]  [112, 276) 'global_node_diff'
[   33.471294]
[   33.472095] The buggy address belongs to the physical page:
[   33.472862] page:3cd72da8 refcount:1 mapcount:0 mapping:00000000 index:0x0 pfn:0x41d03
[   33.473944] flags: 0x1000(reserved|zone=0)
[   33.474565] raw: 00001000 ed741470 ed741470 00000000 00000000 00000000 ffffffff 00000001
[   33.475656] raw: 00000000
[   33.476050] page dumped because: kasan: bad access detected
[   33.476816]
[   33.477061] Memory state around the buggy address:
[   33.477732]  c1d03c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   33.478630]  c1d03c80: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00
[   33.479526] >c1d03d00: 00 04 f2 f2 f2 f2 00 00 00 00 00 00 f1 f1 f1 f1
[   33.480415]                                                ^
[   33.481195]  c1d03d80: 00 00 00 00 00 00 00 00 00 00 04 f3 f3 f3 f3 f3
[   33.482088]  c1d03e00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
[   33.482978] ==================================================================

We find the root cause of this OOB is that arm does not clear stale stack
poison in the case of cpuidle.

This patch refer to arch/arm64/kernel/sleep.S to resolve this issue.

Signed-off-by: Boy Wu <boy.wu@xxxxxxxxxxxx>
---
 arch/arm/kernel/sleep.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index a86a1d4f3461..93afd1005b43 100644
--- a/arch/arm/kernel/sleep.S
+++ b/arch/arm/kernel/sleep.S
@@ -127,6 +127,10 @@ cpu_resume_after_mmu:
 	instr_sync
 #endif
 	bl	cpu_init		@ restore the und/abt/irq banked regs
+#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
+	mov	r0, sp
+	bl	kasan_unpoison_task_stack_below
+#endif
 	mov	r0, #0			@ return zero on success
 	ldmfd	sp!, {r4 - r11, pc}
 ENDPROC(cpu_resume_after_mmu)
-- 
2.18.0