[PATCH] lib: check if stack_table valid in __stack_depot_save

From: zhaoyang.huang
Date: Wed Oct 05 2022 - 21:58:28 EST

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

NULL pointer reported in below lkp test report which should caused by invalid
stack_table in very early stage before stack_depot_early_init called. I would like
have kmemleak use stackdepot to track backtrace in this commit which lead to
stack hash access before stackdepot is initialized. Add stack_table as extra
criteria in __stack_depot_save's entry check.

commit: a65edf711f97a0a3764fc04b0301ab2e073992db ("[PATCH] mm: use stack_depot for recording kmemleak's backtrace")
url: https://github.com/intel-lab-lkp/linux/commits/zhaoyang-huang/mm-use-stack_depot-for-recording-kmemleak-s-backtrace/20220929-183243
base: https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/linux-mm/1664447407-8821-1-git-send-email-zhaoyang.huang@xxxxxxxxxx

in testcase: boot

on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):

[ 0.191645][ T0] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 0.192360][ T0] #PF: supervisor read access in kernel mode
[ 0.192862][ T0] #PF: error_code(0x0000) - not-present page
[ 0.193371][ T0] PGD 0 P4D 0
[ 0.193672][ T0] Oops: 0000 [#1] SMP PTI
[ 0.194051][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.0.0-rc3-00706-ga65edf711f97 #26
[ 0.194755][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014
[ 0.195583][ T0] RIP: 0010:__stack_depot_save (kbuild/src/x86_64-2/lib/stackdepot.c:452)
[ 0.196081][ T0] Code: 03 48 c7 c7 ec 17 b3 84 e8 f1 ea 85 ff 44 89 e0 23 05 d4 aa 01 03 48 8d 04 c3 48 89 c3 48 89 c7 48 89 44 24 28 e8 34 fc 85 ff <4c> 8b 33 4d 85 f6 0f 84 b6 00 00 00 8b 04 24 83 e8 01 48 8d 04 c5
All code
========
0: 03 48 c7 add -0x39(%rax),%ecx
3: c7 (bad)
4: ec in (%dx),%al
5: 17 (bad)
6: b3 84 mov $0x84,%bl
8: e8 f1 ea 85 ff callq 0xffffffffff85eafe
d: 44 89 e0 mov %r12d,%eax
10: 23 05 d4 aa 01 03 and 0x301aad4(%rip),%eax # 0x301aaea
16: 48 8d 04 c3 lea (%rbx,%rax,8),%rax
1a: 48 89 c3 mov %rax,%rbx
1d: 48 89 c7 mov %rax,%rdi
20: 48 89 44 24 28 mov %rax,0x28(%rsp)
25: e8 34 fc 85 ff callq 0xffffffffff85fc5e
2a:* 4c 8b 33 mov (%rbx),%r14 <-- trapping instruction
2d: 4d 85 f6 test %r14,%r14
30: 0f 84 b6 00 00 00 je 0xec
36: 8b 04 24 mov (%rsp),%eax
39: 83 e8 01 sub $0x1,%eax
3c: 48 rex.W
3d: 8d .byte 0x8d
3e: 04 c5 add $0xc5,%al

Code starting with the faulting instruction
===========================================
0: 4c 8b 33 mov (%rbx),%r14
3: 4d 85 f6 test %r14,%r14
6: 0f 84 b6 00 00 00 je 0xc2
c: 8b 04 24 mov (%rsp),%eax
f: 83 e8 01 sub $0x1,%eax
12: 48 rex.W
13: 8d .byte 0x8d
14: 04 c5 add $0xc5,%al
[ 0.197693][ T0] RSP: 0000:ffffffff83603ca8 EFLAGS: 00010046
[ 0.198214][ T0] RAX: ffffffff83613cd8 RBX: 0000000000000000 RCX: ffffffff81b16d2c
[ 0.198858][ T0] RDX: 0000000000000b1e RSI: 0000000000000000 RDI: 0000000000000000
[ 0.199499][ T0] RBP: 00000000c5a6b597 R08: ffffffff8479d118 R09: 0000000000000000
[ 0.200142][ T0] R10: 0000000000000004 R11: 0001ffffffffffff R12: 0000000027b2cd0a
[ 0.200787][ T0] R13: 0000000000000003 R14: 000000004954f68c R15: ffffffff83603d54
[ 0.201488][ T0] FS: 0000000000000000(0000) GS:ffffffff842c9000(0000) knlGS:0000000000000000
[ 0.202247][ T0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.202807][ T0] CR2: 0000000000000000 CR3: 000000000360a000 CR4: 00000000000406b0
[ 0.203470][ T0] Call Trace:
[ 0.203748][ T0] <TASK>
[ 0.203996][ T0] stack_depot_save (kbuild/src/x86_64-2/lib/stackdepot.c:534)
[ 0.204406][ T0] set_track_prepare (kbuild/src/x86_64-2/mm/slub.c:752)
[ 0.204816][ T0] ? memblock_alloc_range_nid (kbuild/src/x86_64-2/mm/memblock.c:1424)
[ 0.205311][ T0] ? memblock_alloc_internal (kbuild/src/x86_64-2/mm/memblock.c:1514)
[ 0.205781][ T0] ? memblock_alloc_try_nid (kbuild/src/x86_64-2/mm/memblock.c:1614 (discriminator 3))
[ 0.206238][ T0] ? setup_command_line (kbuild/src/x86_64-2/init/main.c:631)
[ 0.206670][ T0] ? start_kernel (kbuild/src/x86_64-2/init/main.c:965)
[ 0.207068][ T0] ? secondary_startup_64_no_verify (kbuild/src/x86_64-2/arch/x86/kernel/head_64.S:358)
[ 0.207612][ T0] ? __raw_callee_save___native_queued_spin_unlock (??:?)
[ 0.208251][ T0] ? write_comp_data (kbuild/src/x86_64-2/kernel/kcov.c:236)
[ 0.208678][ T0] ? strncpy (kbuild/src/x86_64-2/lib/string.c:115)
[ 0.209040][ T0] __create_object (kbuild/src/x86_64-2/mm/kmemleak.c:681)
[ 0.209447][ T0] kmemleak_alloc_phys (kbuild/src/x86_64-2/mm/kmemleak.c:1212)
[ 0.209867][ T0] memblock_alloc_range_nid (kbuild/src/x86_64-2/mm/memblock.c:1424)
[ 0.210344][ T0] memblock_alloc_internal (kbuild/src/x86_64-2/mm/memblock.c:1514)
[ 0.210806][ T0] memblock_alloc_try_nid (kbuild/src/x86_64-2/mm/memblock.c:1614 (discriminator 3))
[ 0.211255][ T0] setup_command_line (kbuild/src/x86_64-2/init/main.c:631)
[ 0.211678][ T0] start_kernel (kbuild/src/x86_64-2/init/main.c:965)
[ 0.212063][ T0] ? load_ucode_bsp (kbuild/src/x86_64-2/arch/x86/kernel/cpu/microcode/core.c:176)
[ 0.212483][ T0] secondary_startup_64_no_verify (kbuild/src/x86_64-2/arch/x86/kernel/head_64.S:358)
[ 0.212996][ T0] </TASK>
[ 0.213247][ T0] Modules linked in:
[ 0.213591][ T0] CR2: 0000000000000000
[ 0.213955][ T0] ---[ end trace 0000000000000000 ]---
[ 0.214415][ T0] RIP: 0010:__stack_depot_save (kbuild/src/x86_64-2/lib/stackdepot.c:452)
[ 0.214933][ T0] Code: 03 48 c7 c7 ec 17 b3 84 e8 f1 ea 85 ff 44 89 e0 23 05 d4 aa 01 03 48 8d 04 c3 48 89 c3 48 89 c7 48 89 44 24 28 e8 34 fc 85 ff <4c> 8b 33 4d 85 f6 0f 84 b6 00 00 00 8b 04 24 83 e8 01 48 8d 04 c5

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
lib/stackdepot.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index e73fda2..97b6a2a 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -421,7 +421,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
*/
nr_entries = filter_irq_stacks(entries, nr_entries);

- if (unlikely(nr_entries == 0) || stack_depot_disable)
+ if (unlikely(nr_entries == 0) || stack_depot_disable || !stack_table)
goto fast_exit;

hash = hash_stack(entries, nr_entries);
--
1.9.1