From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
If da_tokens are allocated, but dell_smbios_init() eventually fails, it will
free the da_tokens but it does not reset the da_num_tokens number. This
leads to the possibility of a use after free in dell_smbios_find_token().
As da_tokens is not NULL and da_num_tokens is set to something other than 0.
By reseting the da_num_tokens to zero, and da_tokens to NULL after it is
freed, then access into the other functions that reference them will not
read freed memory.
This was caught by a KASAN report:
==================================================================
BUG: KASAN: use-after-free in dell_smbios_find_token+0x2e/0x80 [dell_smbios]
Read of size 2 at addr ffff88840c2bc1a8 by task systemd-udevd/479
CPU: 0 PID: 479 Comm: systemd-udevd Not tainted 5.1.0-rc1+ #9
Hardware name: Dell Inc. XPS 13 9360/02PG84, BIOS 2.3.1 10/03/2017
Call Trace:
dump_stack+0x7c/0xbb
? dell_smbios_find_token+0x2e/0x80 [dell_smbios]
print_address_description+0xc7/0x280
? dell_smbios_find_token+0x2e/0x80 [dell_smbios]
? dell_smbios_find_token+0x2e/0x80 [dell_smbios]
kasan_report+0x14e/0x192
? dell_smbios_find_token+0x2e/0x80 [dell_smbios]
dell_smbios_find_token+0x2e/0x80 [dell_smbios]
kbd_led_init+0x2e7/0x473 [dell_laptop]
? dmi_matched+0x2a/0x2a [dell_laptop]
? get_device_parent.isra.28+0x2a0/0x2a0
? lockdep_init_map+0x98/0x2c0
? platform_device_add+0x1b5/0x3a0
dell_init+0x4ad/0xb63 [dell_laptop]
? kbd_led_init+0x473/0x473 [dell_laptop]
? ___slab_alloc+0x61f/0x700
? ___slab_alloc+0x61f/0x700
? preempt_count_sub+0x15/0x100
? kbd_led_init+0x473/0x473 [dell_laptop]
do_one_initcall+0xbd/0x3fd
? perf_trace_initcall_level+0x280/0x280
? kasan_unpoison_shadow+0x30/0x40
? __kasan_kmalloc.constprop.8+0xa0/0xd0
? kmem_cache_alloc_trace+0x163/0x390
? kasan_unpoison_shadow+0x30/0x40
do_init_module+0xe3/0x341
load_module+0x2fc5/0x3ad0
? layout_and_allocate+0x1170/0x1170
? vfs_read+0xd4/0x1b0
? kernel_read+0x74/0xa0
? kernel_read_file+0x148/0x320
? seccomp_notify_release+0x110/0x110
? __do_sys_finit_module+0x192/0x1c0
__do_sys_finit_module+0x192/0x1c0
? __ia32_sys_init_module+0x40/0x40
? syscall_trace_enter+0x184/0x5e0
? mark_held_locks+0x1a/0x90
do_syscall_64+0x72/0x220
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fcb4f5f5a49
Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
73 01 c3 48 8b 0d 0f b4 2c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc73e340b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 00005599992bb850 RCX: 00007fcb4f5f5a49
RDX: 0000000000000000 RSI: 00007fcb4f2e11c5 RDI: 0000000000000010
RBP: 00007fcb4f2e11c5 R08: 0000000000000000 R09: 00005599992bb850
R10: 0000000000000010 R11: 0000000000000246 R12: 0000000000000000
R13: 0000559999298f40 R14: 0000000000020000 R15: 00005599992bb850
Allocated by task 479:
__kasan_kmalloc.constprop.8+0xa0/0xd0
krealloc+0xa0/0xc0
0xffffffffc0cc0075
dmi_decode_table+0xf6/0x140
dmi_walk+0x46/0x70
0xffffffffc0cc0109
do_one_initcall+0xbd/0x3fd
do_init_module+0xe3/0x341
load_module+0x2fc5/0x3ad0
__do_sys_finit_module+0x192/0x1c0
do_syscall_64+0x72/0x220
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 479:
__kasan_slab_free+0x111/0x150
kfree+0xf5/0x350
0xffffffffc0cc01d4
do_one_initcall+0xbd/0x3fd
do_init_module+0xe3/0x341
load_module+0x2fc5/0x3ad0
__do_sys_finit_module+0x192/0x1c0
do_syscall_64+0x72/0x220
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff88840c2bc1a8
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 0 bytes inside of
2048-byte region [ffff88840c2bc1a8, ffff88840c2bc9a8)
The buggy address belongs to the page:
page:ffffea001030ae00 count:1 mapcount:0 mapping:ffff8884204113c0 index:0x0
compound_mapcount: 0
flags: 0x17ffffc0010200(slab|head)
raw: 0017ffffc0010200 ffffea0010367608 ffffea000ea31808 ffff8884204113c0
raw: 0000000000000000 00000000000d000d 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88840c2bc080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88840c2bc100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88840c2bc180: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb
^
ffff88840c2bc200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88840c2bc280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Link: http://lkml.kernel.org/r/1553106560.2080.5.camel@xxxxxxxxx
Reported-by: Tom Zanussi <tzanussi@xxxxxxxxx>
Tested-by: Tom Zanussi <tzanussi@xxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
drivers/platform/x86/dell-smbios-base.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/platform/x86/dell-smbios-base.c b/drivers/platform/x86/dell-smbios-base.c
index 0537d44d45a6..a74c0df25b15 100644
--- a/drivers/platform/x86/dell-smbios-base.c
+++ b/drivers/platform/x86/dell-smbios-base.c
@@ -625,6 +625,8 @@ static int __init dell_smbios_init(void)
fail_platform_driver:
kfree(da_tokens);
+ da_tokens = NULL;
+ da_num_tokens = 0;
return ret;
}
--
2.20.1
