[PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Yang Yingliang]

I got a slab-out-of-bounds report when I doing fuzz test.

[  334.989515] ==================================================================
[  334.989577] BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed
[  334.989588] Write of size 1766 at addr ffff8883de69ff3e by task test/2658
[  334.989593]
[  334.989608] CPU: 3 PID: 2658 Comm: test Not tainted 5.7.0-rc5-00005-g152036d1379f #789
[  334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
[  334.989624] Call Trace:
[  334.989646]  dump_stack+0xe4/0x14e
[  334.989676]  print_address_description.constprop.5+0x3f/0x60
[  334.989699]  ? vgacon_scroll+0x57a/0x8ed
[  334.989710]  __kasan_report.cold.8+0x92/0xaf
[  334.989735]  ? vgacon_scroll+0x57a/0x8ed
[  334.989761]  kasan_report+0x37/0x50
[  334.989789]  check_memory_region+0x1c1/0x1e0
[  334.989806]  memcpy+0x38/0x60
[  334.989824]  vgacon_scroll+0x57a/0x8ed
[  334.989876]  con_scroll+0x4ef/0x5e0
[  334.989904]  ? lockdep_hardirqs_on+0x5e0/0x5e0
[  334.989934]  lf+0x24f/0x2a0
[  334.989951]  ? con_scroll+0x5e0/0x5e0
[  334.989975]  ? find_held_lock+0x33/0x1c0
[  334.990005]  do_con_trol+0x313/0x5ff0
[  334.990027]  ? lock_downgrade+0x730/0x730
[  334.990045]  ? reset_palette+0x440/0x440
[  334.990070]  ? _raw_spin_unlock_irqrestore+0x4b/0x60
[  334.990095]  ? notifier_call_chain+0x120/0x170
[  334.990132]  ? __atomic_notifier_call_chain+0xf0/0x180
[  334.990160]  do_con_write.part.16+0xb2b/0x1b20
[  334.990238]  ? do_con_trol+0x5ff0/0x5ff0
[  334.990258]  ? mutex_lock_io_nested+0x1280/0x1280
[  334.990269]  ? rcu_read_unlock+0x50/0x50
[  334.990315]  ? __mutex_unlock_slowpath+0xd9/0x670
[  334.990340]  ? lockdep_hardirqs_on+0x3a2/0x5e0
[  334.990368]  con_write+0x36/0xc0
[  334.990389]  do_output_char+0x561/0x780
[  334.990414]  n_tty_write+0x58e/0xd30
[  334.990478]  ? n_tty_read+0x1800/0x1800
[  334.990500]  ? prepare_to_wait_exclusive+0x300/0x300
[  334.990525]  ? __might_fault+0x17a/0x1c0
[  334.990557]  tty_write+0x430/0x960
[  334.990568]  ? n_tty_read+0x1800/0x1800
[  334.990600]  ? tty_release+0x1280/0x1280
[  334.990622]  __vfs_write+0x81/0x100
[  334.990648]  vfs_write+0x1ce/0x510
[  334.990676]  ksys_write+0x104/0x200
[  334.990691]  ? __ia32_sys_read+0xb0/0xb0
[  334.990708]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[  334.990725]  ? trace_hardirqs_off_caller+0x40/0x1a0
[  334.990744]  ? do_syscall_64+0x3b/0x5e0
[  334.990775]  do_syscall_64+0xc8/0x5e0
[  334.990798]  entry_SYSCALL_64_after_hwframe+0x49/0xb3
[  334.990811] RIP: 0033:0x44f369
[  334.990827] Code: 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
[  334.990834] RSP: 002b:00007ffe9ace0968 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  334.990848] RAX: ffffffffffffffda RBX: 0000000000400418 RCX: 000000000044f369
[  334.990856] RDX: 0000000000000381 RSI: 0000000020003500 RDI: 0000000000000003
[  334.990865] RBP: 00007ffe9ace0980 R08: 0000000020003530 R09: 00007ffe9ace0980
[  334.990873] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000402110
[  334.990881] R13: 0000000000000000 R14: 00000000006bf018 R15: 0000000000000000
[  334.990937]
[  334.990943] The buggy address belongs to the page:
[  334.990962] page:ffffea000f79a400 refcount:1 mapcount:0 mapping:000000002bff47b3 index:0x0 head:ffffea000f79a400 order:4 compound_mapcount:0 compound_pincount:0
[  334.990973] flags: 0x2fffff80010000(head)
[  334.990992] raw: 002fffff80010000 dead000000000100 dead000000000122 0000000000000000
[  334.991006] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
[  334.991013] page dumped because: kasan: bad access detected
[  334.991017]
[  334.991023] Memory state around the buggy address:
[  334.991034]  ffff8883de6a0000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[  334.991044]  ffff8883de6a0080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[  334.991054] >ffff8883de6a0100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
[  334.991061]                                                              ^
[  334.991071]  ffff8883de6a0180: fc fc fc fc fc fc 00 00 00 00 00 00 00 00 00 00
[  334.991082]  ffff8883de6a0200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[  334.991088] ==================================================================

Because vgacon_scrollback_cur->tail plus memcpy size is greater than
vgacon_scrollback_cur->size. Fix this by checking the memcpy size.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/video/console/vgacon.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 998b0de1812f..b51ffb9a208d 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void)
 static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
 {
 	void *p;
+	int size;
 
 	if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size ||
 	    c->vc_num != fg_console)
@@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
 	p = (void *) (c->vc_origin + t * c->vc_size_row);
 
 	while (count--) {
+		size = vgacon_scrollback_cur->size - vgacon_scrollback_cur->tail;
+		if (size > c->vc_size_row)
+			size = c->vc_size_row;
+
 		scr_memcpyw(vgacon_scrollback_cur->data +
 			    vgacon_scrollback_cur->tail,
-			    p, c->vc_size_row);
+			    p, size);
 
 		vgacon_scrollback_cur->cnt++;
-		p += c->vc_size_row;
-		vgacon_scrollback_cur->tail += c->vc_size_row;
+		p += size;
+		vgacon_scrollback_cur->tail += size;
 
 		if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
 			vgacon_scrollback_cur->tail = 0;
-- 
2.25.1

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Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Jiri Slaby]

On 13. 07. 20, 12:57, Yang Yingliang wrote:
> I got a slab-out-of-bounds report when I doing fuzz test.
> 
> [  334.989515] ==================================================================
> [  334.989577] BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed
> [  334.989588] Write of size 1766 at addr ffff8883de69ff3e by task test/2658
> [  334.989593]
> [  334.989608] CPU: 3 PID: 2658 Comm: test Not tainted 5.7.0-rc5-00005-g152036d1379f #789
> [  334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
> [  334.989624] Call Trace:
> [  334.989646]  dump_stack+0xe4/0x14e
> [  334.989676]  print_address_description.constprop.5+0x3f/0x60
> [  334.989699]  ? vgacon_scroll+0x57a/0x8ed
> [  334.989710]  __kasan_report.cold.8+0x92/0xaf
> [  334.989735]  ? vgacon_scroll+0x57a/0x8ed
> [  334.989761]  kasan_report+0x37/0x50
> [  334.989789]  check_memory_region+0x1c1/0x1e0
> [  334.989806]  memcpy+0x38/0x60
> [  334.989824]  vgacon_scroll+0x57a/0x8ed
> [  334.989876]  con_scroll+0x4ef/0x5e0
...
> Because vgacon_scrollback_cur->tail plus memcpy size is greater than
> vgacon_scrollback_cur->size. Fix this by checking the memcpy size.
> 
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  drivers/video/console/vgacon.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index 998b0de1812f..b51ffb9a208d 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void)
>  static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
>  {
>  	void *p;
> +	int size;
>  
>  	if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size ||
>  	    c->vc_num != fg_console)
> @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
>  	p = (void *) (c->vc_origin + t * c->vc_size_row);
>  
>  	while (count--) {
> +		size = vgacon_scrollback_cur->size - vgacon_scrollback_cur->tail;
> +		if (size > c->vc_size_row)
> +			size = c->vc_size_row;
> +
>  		scr_memcpyw(vgacon_scrollback_cur->data +
>  			    vgacon_scrollback_cur->tail,
> -			    p, c->vc_size_row);
> +			    p, size);

Are you sure the consumer can handle split lines? As vgacon_scrolldelta
(soff in particular) looks to me like it doesn't.

Have you tested you patch? I mean with soft scrollback on the vga console?

>  		vgacon_scrollback_cur->cnt++;
> -		p += c->vc_size_row;
> -		vgacon_scrollback_cur->tail += c->vc_size_row;
> +		p += size;
> +		vgacon_scrollback_cur->tail += size;
>  
>  		if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
>  			vgacon_scrollback_cur->tail = 0;
> 

thanks,
-- 
js
suse labs
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Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Yang Yingliang]

On 2020/7/30 19:04, Jiri Slaby wrote:
> On 13. 07. 20, 12:57, Yang Yingliang wrote:
>> I got a slab-out-of-bounds report when I doing fuzz test.
>>
>> [  334.989515] ==================================================================
>> [  334.989577] BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed
>> [  334.989588] Write of size 1766 at addr ffff8883de69ff3e by task test/2658
>> [  334.989593]
>> [  334.989608] CPU: 3 PID: 2658 Comm: test Not tainted 5.7.0-rc5-00005-g152036d1379f #789
>> [  334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
>> [  334.989624] Call Trace:
>> [  334.989646]  dump_stack+0xe4/0x14e
>> [  334.989676]  print_address_description.constprop.5+0x3f/0x60
>> [  334.989699]  ? vgacon_scroll+0x57a/0x8ed
>> [  334.989710]  __kasan_report.cold.8+0x92/0xaf
>> [  334.989735]  ? vgacon_scroll+0x57a/0x8ed
>> [  334.989761]  kasan_report+0x37/0x50
>> [  334.989789]  check_memory_region+0x1c1/0x1e0
>> [  334.989806]  memcpy+0x38/0x60
>> [  334.989824]  vgacon_scroll+0x57a/0x8ed
>> [  334.989876]  con_scroll+0x4ef/0x5e0
> ...
>> Because vgacon_scrollback_cur->tail plus memcpy size is greater than
>> vgacon_scrollback_cur->size. Fix this by checking the memcpy size.
>>
>> Reported-by: Hulk Robot <hulkci@huawei.com>
>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   drivers/video/console/vgacon.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
>> index 998b0de1812f..b51ffb9a208d 100644
>> --- a/drivers/video/console/vgacon.c
>> +++ b/drivers/video/console/vgacon.c
>> @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void)
>>   static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
>>   {
>>   	void *p;
>> +	int size;
>>   
>>   	if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size ||
>>   	    c->vc_num != fg_console)
>> @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
>>   	p = (void *) (c->vc_origin + t * c->vc_size_row);
>>   
>>   	while (count--) {
>> +		size = vgacon_scrollback_cur->size - vgacon_scrollback_cur->tail;
>> +		if (size > c->vc_size_row)
>> +			size = c->vc_size_row;
>> +
>>   		scr_memcpyw(vgacon_scrollback_cur->data +
>>   			    vgacon_scrollback_cur->tail,
>> -			    p, c->vc_size_row);
>> +			    p, size);
> Are you sure the consumer can handle split lines? As vgacon_scrolldelta
> (soff in particular) looks to me like it doesn't.
>
> Have you tested you patch? I mean with soft scrollback on the vga console?

I only test the patch with the reproduce program.


Thanks,

Yang

>
>>   		vgacon_scrollback_cur->cnt++;
>> -		p += c->vc_size_row;
>> -		vgacon_scrollback_cur->tail += c->vc_size_row;
>> +		p += size;
>> +		vgacon_scrollback_cur->tail += size;
>>   
>>   		if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
>>   			vgacon_scrollback_cur->tail = 0;
>>
> thanks,

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Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Jiri Slaby]

On 30. 07. 20, 15:24, Yang Yingliang wrote:
> 
> On 2020/7/30 19:04, Jiri Slaby wrote:
>> On 13. 07. 20, 12:57, Yang Yingliang wrote:
>>> I got a slab-out-of-bounds report when I doing fuzz test.
>>>
>>> [  334.989515]
>>> ==================================================================
>>> [  334.989577] BUG: KASAN: slab-out-of-bounds in
>>> vgacon_scroll+0x57a/0x8ed
>>> [  334.989588] Write of size 1766 at addr ffff8883de69ff3e by task
>>> test/2658
>>> [  334.989593]
>>> [  334.989608] CPU: 3 PID: 2658 Comm: test Not tainted
>>> 5.7.0-rc5-00005-g152036d1379f #789
>>> [  334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>>> BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
>>> [  334.989624] Call Trace:
>>> [  334.989646]  dump_stack+0xe4/0x14e
>>> [  334.989676]  print_address_description.constprop.5+0x3f/0x60
>>> [  334.989699]  ? vgacon_scroll+0x57a/0x8ed
>>> [  334.989710]  __kasan_report.cold.8+0x92/0xaf
>>> [  334.989735]  ? vgacon_scroll+0x57a/0x8ed
>>> [  334.989761]  kasan_report+0x37/0x50
>>> [  334.989789]  check_memory_region+0x1c1/0x1e0
>>> [  334.989806]  memcpy+0x38/0x60
>>> [  334.989824]  vgacon_scroll+0x57a/0x8ed
>>> [  334.989876]  con_scroll+0x4ef/0x5e0
>> ...
>>> Because vgacon_scrollback_cur->tail plus memcpy size is greater than
>>> vgacon_scrollback_cur->size. Fix this by checking the memcpy size.
>>>
>>> Reported-by: Hulk Robot <hulkci@huawei.com>
>>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>>> ---
>>>   drivers/video/console/vgacon.c | 11 ++++++++---
>>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/video/console/vgacon.c
>>> b/drivers/video/console/vgacon.c
>>> index 998b0de1812f..b51ffb9a208d 100644
>>> --- a/drivers/video/console/vgacon.c
>>> +++ b/drivers/video/console/vgacon.c
>>> @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void)
>>>   static void vgacon_scrollback_update(struct vc_data *c, int t, int
>>> count)
>>>   {
>>>       void *p;
>>> +    int size;
>>>         if (!vgacon_scrollback_cur->data ||
>>> !vgacon_scrollback_cur->size ||
>>>           c->vc_num != fg_console)
>>> @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct
>>> vc_data *c, int t, int count)
>>>       p = (void *) (c->vc_origin + t * c->vc_size_row);
>>>         while (count--) {
>>> +        size = vgacon_scrollback_cur->size -
>>> vgacon_scrollback_cur->tail;
>>> +        if (size > c->vc_size_row)
>>> +            size = c->vc_size_row;
>>> +
>>>           scr_memcpyw(vgacon_scrollback_cur->data +
>>>                   vgacon_scrollback_cur->tail,
>>> -                p, c->vc_size_row);
>>> +                p, size);
>> Are you sure the consumer can handle split lines? As vgacon_scrolldelta
>> (soff in particular) looks to me like it doesn't.
>>
>> Have you tested you patch? I mean with soft scrollback on the vga
>> console?
> 
> I only test the patch with the reproduce program.

Out of curiosity, what is it doing? Resize and then scroll by \n (line
feed)? Can you share it?

thanks,
-- 
js
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Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Yang Yingliang]

[-- Attachment #1.1: Type: text/plain, Size: 10518 bytes --]


On 2020/7/30 21:38, Jiri Slaby wrote:
> On 30. 07. 20, 15:24, Yang Yingliang wrote:
>> On 2020/7/30 19:04, Jiri Slaby wrote:
>>> On 13. 07. 20, 12:57, Yang Yingliang wrote:
>>>> I got a slab-out-of-bounds report when I doing fuzz test.
>>>>
>>>> [  334.989515]
>>>> ==================================================================
>>>> [  334.989577] BUG: KASAN: slab-out-of-bounds in
>>>> vgacon_scroll+0x57a/0x8ed
>>>> [  334.989588] Write of size 1766 at addr ffff8883de69ff3e by task
>>>> test/2658
>>>> [  334.989593]
>>>> [  334.989608] CPU: 3 PID: 2658 Comm: test Not tainted
>>>> 5.7.0-rc5-00005-g152036d1379f #789
>>>> [  334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>>>> BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
>>>> [  334.989624] Call Trace:
>>>> [  334.989646]  dump_stack+0xe4/0x14e
>>>> [  334.989676]  print_address_description.constprop.5+0x3f/0x60
>>>> [  334.989699]  ? vgacon_scroll+0x57a/0x8ed
>>>> [  334.989710]  __kasan_report.cold.8+0x92/0xaf
>>>> [  334.989735]  ? vgacon_scroll+0x57a/0x8ed
>>>> [  334.989761]  kasan_report+0x37/0x50
>>>> [  334.989789]  check_memory_region+0x1c1/0x1e0
>>>> [  334.989806]  memcpy+0x38/0x60
>>>> [  334.989824]  vgacon_scroll+0x57a/0x8ed
>>>> [  334.989876]  con_scroll+0x4ef/0x5e0
>>> ...
>>>> Because vgacon_scrollback_cur->tail plus memcpy size is greater than
>>>> vgacon_scrollback_cur->size. Fix this by checking the memcpy size.
>>>>
>>>> Reported-by: Hulk Robot <hulkci@huawei.com>
>>>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>>>> ---
>>>>    drivers/video/console/vgacon.c | 11 ++++++++---
>>>>    1 file changed, 8 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/video/console/vgacon.c
>>>> b/drivers/video/console/vgacon.c
>>>> index 998b0de1812f..b51ffb9a208d 100644
>>>> --- a/drivers/video/console/vgacon.c
>>>> +++ b/drivers/video/console/vgacon.c
>>>> @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void)
>>>>    static void vgacon_scrollback_update(struct vc_data *c, int t, int
>>>> count)
>>>>    {
>>>>        void *p;
>>>> +    int size;
>>>>          if (!vgacon_scrollback_cur->data ||
>>>> !vgacon_scrollback_cur->size ||
>>>>            c->vc_num != fg_console)
>>>> @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct
>>>> vc_data *c, int t, int count)
>>>>        p = (void *) (c->vc_origin + t * c->vc_size_row);
>>>>          while (count--) {
>>>> +        size = vgacon_scrollback_cur->size -
>>>> vgacon_scrollback_cur->tail;
>>>> +        if (size > c->vc_size_row)
>>>> +            size = c->vc_size_row;
>>>> +
>>>>            scr_memcpyw(vgacon_scrollback_cur->data +
>>>>                    vgacon_scrollback_cur->tail,
>>>> -                p, c->vc_size_row);
>>>> +                p, size);
>>> Are you sure the consumer can handle split lines? As vgacon_scrolldelta
>>> (soff in particular) looks to me like it doesn't.
>>>
>>> Have you tested you patch? I mean with soft scrollback on the vga
>>> console?
>> I only test the patch with the reproduce program.
> Out of curiosity, what is it doing? Resize and then scroll by \n (line
> feed)? Can you share it?

// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

static void sleep_ms(uint64_t ms)
{
	usleep(ms * 1000);
}

static uint64_t current_time_ms(void)
{
	struct timespec ts;
	if (clock_gettime(CLOCK_MONOTONIC, &ts))
	exit(1);
	return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static bool write_file(const char* file, const char* what, ...)
{
	char buf[1024];
	va_list args;
	va_start(args, what);
	vsnprintf(buf, sizeof(buf), what, args);
	va_end(args);
	buf[sizeof(buf) - 1] = 0;
	int len = strlen(buf);
	int fd = open(file, O_WRONLY | O_CLOEXEC);
	if (fd == -1)
		return false;
	if (write(fd, buf, len) != len) {
		int err = errno;
		close(fd);
		errno = err;
		return false;
	}
	close(fd);
	return true;
}

static long syz_open_dev(volatile long a0, volatile long a1, volatile long a2)
{
	if (a0 == 0xc || a0 == 0xb) {
		char buf[128];
		sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1, (uint8_t)a2);
		return open(buf, O_RDWR, 0);
	} else {
		char buf[1024];
		char* hash;
strncpy(buf, (char*)a0, sizeof(buf) - 1);
		buf[sizeof(buf) - 1] = 0;
		while ((hash = strchr(buf, '#'))) {
			*hash = '0' + (char)(a1 % 10);
			a1 /= 10;
		}
		return open(buf, a2, 0);
	}
}

static void kill_and_wait(int pid, int* status)
{
	kill(-pid, SIGKILL);
	kill(pid, SIGKILL);
	int i;
	for (i = 0; i < 100; i++) {
		if (waitpid(-1, status, WNOHANG | __WALL) == pid)
			return;
		usleep(1000);
	}
	DIR* dir = opendir("/sys/fs/fuse/connections");
	if (dir) {
		for (;;) {
			struct dirent* ent = readdir(dir);
			if (!ent)
				break;
			if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
				continue;
			char abort[300];
			snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort", ent->d_name);
			int fd = open(abort, O_WRONLY);
			if (fd == -1) {
				continue;
			}
			if (write(fd, abort, 1) < 0) {
			}
			close(fd);
		}
		closedir(dir);
	} else {
	}
	while (waitpid(-1, status, __WALL) != pid) {
	}
}

static void setup_test()
{
	prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
	setpgrp();
	write_file("/proc/self/oom_score_adj", "1000");
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void)
{
	int iter;
	for (iter = 0;; iter++) {
		int pid = fork();
		if (pid < 0)
	exit(1);
		if (pid == 0) {
			setup_test();
			execute_one();
			exit(0);
		}
		int status = 0;
		uint64_t start = current_time_ms();
		for (;;) {
			if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
				break;
			sleep_ms(1);
			if (current_time_ms() - start < 5 * 1000)
				continue;
			kill_and_wait(pid, &status);
			break;
		}
	}
}

uint64_t r[1] = {0xffffffffffffffff};

void execute_one(void)
{
		intptr_t res = 0;
	res = syz_open_dev(0xc, 4, 1);
	if (res != -1)
		r[0] = res;
*(uint16_t*)0x20000000 = 0xc;
*(uint16_t*)0x20000002 = 0x373;
*(uint16_t*)0x20000004 = 0x1442;
	syscall(__NR_ioctl, r[0], 0x5609ul, 0x20000000ul);
memcpy((void*)0x20003500, "\x7f\x45\x4c\x46\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x38\x00\x00\x00\x00\x00\x00\x00\x01\x04\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x69\x2e\x77\x3d\x64\xf5\xe4\xb9\xaf\x86\xb6\xcb\x74\x6e\xe0\x71\x3a\xfb\x18\x4e\xb2\xb9\x99\x36\xd4\x71\x6d\xbf\xfc\x0d\xfb\xec\x4b\x82\x2d\xde\xa8\xb8\x79\x34\xcc\xe8\x11\x28\x49\x27\xb5\xe6\xeb\x37\x33\x73\xad\x27\x6b\xfd\x68\x18\x46\x9e\x3a\x35\xd0\x5b\x6f\x2f\xd5\x8a\x88\x96\xd0\x65\x16\x70\x95\x10\x0f\x97\xb8\xe6\x71\x60\x87\xcb\xf2\x92\x60\x4b\x89\x8a\xb8\xcf\x95\x85\x67\xef\x4e\xf3\xa8\x8e\xd4\x9f\x81\x83\x0a\x85\x54\x45\xff\x6c\xbd\xa4\xca\x4e\xae\x3d\x65\xef\x15\x76\xa2\x90\x16\xdb\xe3\xc9\x9c\x78\x30\x1e\x04\x8c\x17\x17\x06\xb3\x06\xc4\x87\x12\xc3\xe2\x5a\xb5\x83\x8a\xe3\x1e\x7d\xe1\xf1\xdc\x95\x79\xa7\x1c\xcb\x39\xf6\x05\x1e\xed\xd7\xf0\xb5\xa7\xc8\xb6\xfc\x41\xf4\x2d\x3e\x67\xba\xe8\xe4\x86\xa6\x31\x1e\xf2\x49\xda\x11\x41\xab\xfd\xc1\x0a\xe5\x69\x6b\xdb\xad\x95\xe4\x53\xb9\x37\xce\x6d\xad\x22\x39\xab\xd7\x9f\xcf\xa1\xdc\x84\xd7\x3b\xc2\xa3\xc6\xc3\x73\xa9\xd5\x3e\xf0\x01\xff\x18\x76\xe6\x47\xf4\x1b\x6a\x96\x8d\xc4\x9f\xe7\xc2\x93\x8a\x3d\xf9\x9b\xfd\x79\x5b\x7d\x2d\xb4\x82\x78\x38\x0f\x6b\xd0\xdc\xd2\x8b\x8e\xfe\xc1\xcf\xd5\x03\x98\x86\x7e\xf3\x29\xee\x1c\xb7\x34\xc1\x2f\xce\x5b\x51\x29\x2b\xe4\xef\xe7\x5e\x0d\x3f\x57\x8c\xc9\x89\xea\x55\xa0\x65\x00\x00\x00\x00\x00\x00\x00\x6f\x7e\x76\xa2\x37\x0e\x3e\x0b\x83\xa2\x6a\x88\x95\xa6\xac\x75\x4b\xee\xc4\x42\x87\xfa\xfd\x91\x3d\x6a\x4d\x92\x10\x71\x7c\xec\xaa\x58\x90\xbf\xa7\x5c\x72\xfd\x89\x6d\xb3\x07\x0f\xd2\x35\xd3\xdf\x78\x32\x51\x2f\x88\x03\x0e\x1d\x1c\xd5\xf3\x27\xa0\xe1\xd4\xc1\x05\xf7\x2d\xd1\x31\x87\x40\x7e\x92\x11\x28\xc5\x54\xb8\x49\x16\x6d\xdc\x79\xed\x21\xa4\x33\x7d\xdf\x56\x94\xad\xcf\x69\xd0\xb9\xb4\x6b\x6a\x67\x5c\x9d\x23\x1a\xec\xf2\x73\x03\xd2\x13\xf1\xdb\xe8\xb4\x79\x18\xd1\x50\x49\xc1\xd5\x85\xec\x84\xcd\x37\x0b\xed\x7b\xce\x6b\x31\x36\x1e\xfb\x69\x9d\xa8\xc2\x66\x65\x86\x9b\x25\x97\x1d\x59\x7c\x9c\x82\xe5\xe4\x1b\xd7\xe7\xb7\xda\xd8\x2a\x64\x96\xaf\xa7\x84\x40\x33\x97\x7a\x5a\xc0\x1f\x8c\xca\x91\x12\x94\x74\xb2\x5f\x25\xd1\xf1\xa2\x17\x87\x52\x89\x30\x2b\x3f\xf6\x45\x58\x31\x6e\x68\xa3\x5e\xd2\xa3\x80\xf7\xf0\xaf\x03\x9d\x1b\x33\xe8\x4e\x11\xf4\x19\x69\x8f\xc3\x0d\x0a\x72\xa3\xab\xb7\x66\xb1\x3b\xc4\x29\x58\x22\x0f\xae\xfc\x68\xcc\x66\x9b\x62\x4c\xc8\xce\x7e\xdc\xe5\x65\xbc\xc3\xde\xdc\x6f\xe4\x81\xd4\x4a\xd7\x0f\x37\xb7\x8f\x36\x89\x85\x6b\x0d\xb9\xe5\x4c\xc1\xfd\xd7\x1a\xa6\xc7\x0d\xf3\x8d\xcb\x5a\x9a\x6a\xea\x39\xf5\xe1\x42\xc7\x8a\xdc\x2e\x61\xb1\x4f\xea\x20\xd0\x0d\x50\x08\xc2\xbe\x36\xe5\xc0\x67\xe2\x43\x1d\x39\xbd\xda\x47\xa4\xb3\x59\xb3\x2d\x6a\x7e\x3a\xbc\xa7\x53\xf0\x46\x61\xe6\x9c\xef\xcf\xad\x50\x79\x5b\xb0\xd9\x40\xba\xb3\x5e\xf9\x39\xee\x9e\xe0\xfe\xfc\x59\x14\xac\x60\xcf\xcb\x9e\x7a\x47\x6f\xda\x4c\x09\x9e\xa1\x15\x24\x9a\x40\xf2\xe5\x34\xf4\x80\x03\x63\x08\x13\xe1\xab\xa9\xc2\x59\x15\x00\xe3\xc3\xe2\xa9\x0d\x5f\x0f\xa4\x53\x63\xbd\x72\xdc\xc9\xc2\x13\xc0\x0a\xbd\x7c\xec\xa8\x2d\x16\xac\x65\xf3\x58\xca\x62\x6c\x07\xba\x01\x72\xfa\x5a\xbe\x68\xfe\x92\xbe\xa2\xc7\xdc\xc6\xcd\xab\x10\x58\x4a\x9d\x2e\x61\x85\x56\x9f\x0e\x74\x6c\x49\xf8\x3d\x43\x43\x4f\xd3\x93\xf3\x1d\xcb\x31\x4c\xf6\x78\xed\x4b\x76\x1f\x46\x58\x58\x05\x9a\x59\x7d\xf9\x28\x0c\x7a\x49\x04\x6c\xda\x7e\x96\xe0\x22\x90\x64\x0d\xfa\x8f\xbd\xf1\xdb\x74\x75\x2d\x79\xe5\x20\x38\x8f\x0a\x20\xe8\x09\x31\xd6\x7a\x5b\xbb\x86\x9b\x38\x6d", 897);
	syscall(__NR_write, r[0], 0x20003500ul, 0x381ul);

}
int main(void)
{
		syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 3ul, 0x32ul, -1, 0);
			loop();
	return 0;
}

>
> thanks,

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Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update()

[Jiri Slaby]

Hi,

On 31. 07. 20, 5:23, Yang Yingliang wrote:
> void execute_one(void)
> {
> 		intptr_t res = 0;
> 	res = syz_open_dev(0xc, 4, 1);

open(/dev/tty1)

> 	if (res != -1)
> 		r[0] = res;
> *(uint16_t*)0x20000000 = 0xc;
> *(uint16_t*)0x20000002 = 0x373;
> *(uint16_t*)0x20000004 = 0x1442;
> 	syscall(__NR_ioctl, r[0], 0x5609ul, 0x20000000ul);

VT_RESIZE(12, 883)

> memcpy((void*)0x20003500, "\x7f\x45\x4c\x46\x00\x00\x00...
> 	syscall(__NR_write, r[0], 0x20003500ul, 0x381ul);

Write 381 bytes of some ELF to the tty.

OK, that's it. Thanks.

-- 
js
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