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* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-29 12:06 syzbot
  2019-04-29 20:07 ` Alan Stern
  0 siblings, 1 reply; 12+ messages in thread
From: syzbot @ 2019-04-29 12:06 UTC (permalink / raw)
  To: andreyknvl, gregkh, linux-kernel, linux-usb, rafael, syzkaller-bugs

Hello,

syzbot found the following crash on:

HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan/tree/usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12

CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xe8/0x16e lib/dump_stack.c:113
  print_address_description+0x6c/0x236 mm/kasan/report.c:187
  kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
  hex_string+0x418/0x4b0 lib/vsprintf.c:975
  pointer+0x460/0x910 lib/vsprintf.c:1985
  vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
  pointer+0x60b/0x910 lib/vsprintf.c:2038
  vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
  vscnprintf+0x29/0x80 lib/vsprintf.c:2499
  vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
  vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
  dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
  dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
  __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
  _dev_info+0xdc/0x10e drivers/base/core.c:3254
  dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
  dlfb_usb_probe.cold+0xb96/0x1701 drivers/video/fbdev/udlfb.c:1615
  usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361
  really_probe+0x2da/0xb10 drivers/base/dd.c:509
  driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
  __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
  bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
  __device_attach+0x223/0x3a0 drivers/base/dd.c:844
  bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
  device_add+0xad2/0x16e0 drivers/base/core.c:2106
  usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2023
  generic_probe+0xa2/0xda drivers/usb/core/generic.c:210
  usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266
  really_probe+0x2da/0xb10 drivers/base/dd.c:509
  driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
  __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
  bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
  __device_attach+0x223/0x3a0 drivers/base/dd.c:844
  bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
  device_add+0xad2/0x16e0 drivers/base/core.c:2106
  usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534
  hub_port_connect drivers/usb/core/hub.c:5089 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
  port_event drivers/usb/core/hub.c:5350 [inline]
  hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
  process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
  worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
  kthread+0x313/0x420 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Allocated by task 12:
  set_track mm/kasan/common.c:87 [inline]
  __kasan_kmalloc mm/kasan/common.c:497 [inline]
  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:470
  kmalloc include/linux/slab.h:552 [inline]
  usb_get_configuration+0x313/0x32b0 drivers/usb/core/config.c:857
  usb_enumerate_device drivers/usb/core/hub.c:2367 [inline]
  usb_new_device+0x2fe/0x450 drivers/usb/core/hub.c:2503
  hub_port_connect drivers/usb/core/hub.c:5089 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
  port_event drivers/usb/core/hub.c:5350 [inline]
  hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
  process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
  worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
  kthread+0x313/0x420 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Freed by task 1464:
  set_track mm/kasan/common.c:87 [inline]
  __kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
  slab_free_hook mm/slub.c:1429 [inline]
  slab_free_freelist_hook+0x5e/0x140 mm/slub.c:1456
  slab_free mm/slub.c:3003 [inline]
  kfree+0xce/0x290 mm/slub.c:3958
  single_release+0x91/0xb0 fs/seq_file.c:597
  __fput+0x2df/0x8c0 fs/file_table.c:278
  task_work_run+0x149/0x1c0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x243/0x270 arch/x86/entry/common.c:166
  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
  do_syscall_64+0x40c/0x4f0 arch/x86/entry/common.c:293
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88821a41bd20
  which belongs to the cache kmalloc-32 of size 32
The buggy address is located 24 bytes inside of
  32-byte region [ffff88821a41bd20, ffff88821a41bd40)
The buggy address belongs to the page:
page:ffffea00086906c0 count:1 mapcount:0 mapping:ffff88812c3f5800 index:0x0
flags: 0x57ff00000000200(slab)
raw: 057ff00000000200 dead000000000100 dead000000000200 ffff88812c3f5800
raw: 0000000000000000 0000000000550055 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88821a41bc00: 00 00 00 fc fc fc 00 00 00 00 fc fc 00 00 00 00
  ffff88821a41bc80: fc fc 00 00 00 00 fc fc fb fb fb fb fc fc fb fb
> ffff88821a41bd00: fb fb fc fc 00 00 00 fc fc fc fb fb fb fb fc fc
                                         ^
  ffff88821a41bd80: 00 00 00 fc fc fc 00 00 00 fc fc fc fb fb fb fb
  ffff88821a41be00: fc fc fb fb fb fb fc fc fb fb fb fb fc fc 00 00
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

^ permalink raw reply	[flat|nested] 12+ messages in thread

* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-29 20:07 ` Alan Stern
  2019-04-29 20:07   ` Alan Stern
                     ` (3 more replies)
  0 siblings, 4 replies; 12+ messages in thread
From: Alan Stern @ 2019-04-29 20:07 UTC (permalink / raw)
  To: syzbot
  Cc: andreyknvl, gregkh, linux-kernel, linux-usb, rafael, syzkaller-bugs

On Mon, 29 Apr 2019, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> 
> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xe8/0x16e lib/dump_stack.c:113
>   print_address_description+0x6c/0x236 mm/kasan/report.c:187
>   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
>   hex_string+0x418/0x4b0 lib/vsprintf.c:975
>   pointer+0x460/0x910 lib/vsprintf.c:1985
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   pointer+0x60b/0x910 lib/vsprintf.c:2038
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
>   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
>   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
>   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
>   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
>   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
>   _dev_info+0xdc/0x10e drivers/base/core.c:3254
>   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]

Accessing beyond the end of the descriptor.

#syz test: https://github.com/google/kasan.git usb-fuzzer

--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
 	char *buf;
 	char *desc_end;
 	int total_len;
+	int width;
 
 	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
 	if (!buf)
@@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
 	}
 
 	if (total_len > 5) {
+		width = min(total_len, 11);
 		dev_info(&intf->dev,
-			 "vendor descriptor length: %d data: %11ph\n",
-			 total_len, desc);
+			 "vendor descriptor length: %d data: %*ph\n",
+			 total_len, width, desc);
 
 		if ((desc[0] != total_len) || /* descriptor length */
 		    (desc[1] != 0x5f) ||   /* vendor descriptor type */

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-29 20:07 ` Alan Stern
@ 2019-04-29 20:07   ` Alan Stern
  2019-04-29 20:24   ` Andrey Konovalov
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 12+ messages in thread
From: Alan Stern @ 2019-04-29 20:07 UTC (permalink / raw)
  To: syzbot
  Cc: andreyknvl, gregkh, linux-kernel, linux-usb, rafael, syzkaller-bugs

On Mon, 29 Apr 2019, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> 
> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xe8/0x16e lib/dump_stack.c:113
>   print_address_description+0x6c/0x236 mm/kasan/report.c:187
>   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
>   hex_string+0x418/0x4b0 lib/vsprintf.c:975
>   pointer+0x460/0x910 lib/vsprintf.c:1985
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   pointer+0x60b/0x910 lib/vsprintf.c:2038
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
>   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
>   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
>   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
>   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
>   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
>   _dev_info+0xdc/0x10e drivers/base/core.c:3254
>   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]

Accessing beyond the end of the descriptor.

#syz test: https://github.com/google/kasan.git usb-fuzzer

--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
 	char *buf;
 	char *desc_end;
 	int total_len;
+	int width;
 
 	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
 	if (!buf)
@@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
 	}
 
 	if (total_len > 5) {
+		width = min(total_len, 11);
 		dev_info(&intf->dev,
-			 "vendor descriptor length: %d data: %11ph\n",
-			 total_len, desc);
+			 "vendor descriptor length: %d data: %*ph\n",
+			 total_len, width, desc);
 
 		if ((desc[0] != total_len) || /* descriptor length */
 		    (desc[1] != 0x5f) ||   /* vendor descriptor type */



^ permalink raw reply	[flat|nested] 12+ messages in thread

* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-29 20:24   ` Andrey Konovalov
  2019-04-29 20:24     ` Andrey Konovalov
  0 siblings, 1 reply; 12+ messages in thread
From: Andrey Konovalov @ 2019-04-29 20:24 UTC (permalink / raw)
  To: Alan Stern
  Cc: syzbot, Greg Kroah-Hartman, LKML, USB list, rafael, syzkaller-bugs

On Mon, Apr 29, 2019 at 10:07 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Mon, 29 Apr 2019, syzbot wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> >
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> > Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> >
> > CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0xe8/0x16e lib/dump_stack.c:113
> >   print_address_description+0x6c/0x236 mm/kasan/report.c:187
> >   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
> >   hex_string+0x418/0x4b0 lib/vsprintf.c:975
> >   pointer+0x460/0x910 lib/vsprintf.c:1985
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   pointer+0x60b/0x910 lib/vsprintf.c:2038
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
> >   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
> >   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
> >   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
> >   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
> >   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
> >   _dev_info+0xdc/0x10e drivers/base/core.c:3254
> >   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
>
> Accessing beyond the end of the descriptor.
>
> #syz test: https://github.com/google/kasan.git usb-fuzzer

Hi Alan,

Thanks for the patch!

syzbot should now be able to understand the quilt patch format that
you use, feel free to give it a try next time :)

>
> --- a/drivers/video/fbdev/udlfb.c
> +++ b/drivers/video/fbdev/udlfb.c
> @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
>         char *buf;
>         char *desc_end;
>         int total_len;
> +       int width;
>
>         buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
>         if (!buf)
> @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
>         }
>
>         if (total_len > 5) {
> +               width = min(total_len, 11);
>                 dev_info(&intf->dev,
> -                        "vendor descriptor length: %d data: %11ph\n",
> -                        total_len, desc);
> +                        "vendor descriptor length: %d data: %*ph\n",
> +                        total_len, width, desc);
>
>                 if ((desc[0] != total_len) || /* descriptor length */
>                     (desc[1] != 0x5f) ||   /* vendor descriptor type */
>
>

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-29 20:24   ` Andrey Konovalov
@ 2019-04-29 20:24     ` Andrey Konovalov
  0 siblings, 0 replies; 12+ messages in thread
From: Andrey Konovalov @ 2019-04-29 20:24 UTC (permalink / raw)
  To: Alan Stern
  Cc: syzbot, Greg Kroah-Hartman, LKML, USB list, rafael, syzkaller-bugs

On Mon, Apr 29, 2019 at 10:07 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Mon, 29 Apr 2019, syzbot wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> >
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> > Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> >
> > CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0xe8/0x16e lib/dump_stack.c:113
> >   print_address_description+0x6c/0x236 mm/kasan/report.c:187
> >   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
> >   hex_string+0x418/0x4b0 lib/vsprintf.c:975
> >   pointer+0x460/0x910 lib/vsprintf.c:1985
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   pointer+0x60b/0x910 lib/vsprintf.c:2038
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
> >   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
> >   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
> >   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
> >   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
> >   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
> >   _dev_info+0xdc/0x10e drivers/base/core.c:3254
> >   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
>
> Accessing beyond the end of the descriptor.
>
> #syz test: https://github.com/google/kasan.git usb-fuzzer

Hi Alan,

Thanks for the patch!

syzbot should now be able to understand the quilt patch format that
you use, feel free to give it a try next time :)

>
> --- a/drivers/video/fbdev/udlfb.c
> +++ b/drivers/video/fbdev/udlfb.c
> @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
>         char *buf;
>         char *desc_end;
>         int total_len;
> +       int width;
>
>         buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
>         if (!buf)
> @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
>         }
>
>         if (total_len > 5) {
> +               width = min(total_len, 11);
>                 dev_info(&intf->dev,
> -                        "vendor descriptor length: %d data: %11ph\n",
> -                        total_len, desc);
> +                        "vendor descriptor length: %d data: %*ph\n",
> +                        total_len, width, desc);
>
>                 if ((desc[0] != total_len) || /* descriptor length */
>                     (desc[1] != 0x5f) ||   /* vendor descriptor type */
>
>

^ permalink raw reply	[flat|nested] 12+ messages in thread

* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-29 20:52   ` syzbot
  2019-04-29 20:52     ` syzbot
  0 siblings, 1 reply; 12+ messages in thread
From: syzbot @ 2019-04-29 20:52 UTC (permalink / raw)
  To: andreyknvl, gregkh, linux-kernel, linux-usb, rafael, stern,
	syzkaller-bugs

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger  
crash:

Reported-and-tested-by:  
syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com

Tested on:

commit:         43151d6c usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16c59788a00000

Note: testing is done by a robot and is best-effort only.

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-29 20:52   ` syzbot
@ 2019-04-29 20:52     ` syzbot
  0 siblings, 0 replies; 12+ messages in thread
From: syzbot @ 2019-04-29 20:52 UTC (permalink / raw)
  To: andreyknvl, gregkh, linux-kernel, linux-usb, rafael, stern,
	syzkaller-bugs

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger  
crash:

Reported-and-tested-by:  
syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com

Tested on:

commit:         43151d6c usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16c59788a00000

Note: testing is done by a robot and is best-effort only.

^ permalink raw reply	[flat|nested] 12+ messages in thread

* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-29 21:09   ` Eric Biggers
  2019-04-29 21:09     ` Eric Biggers
  2019-04-30 14:13     ` Alan Stern
  0 siblings, 2 replies; 12+ messages in thread
From: Eric Biggers @ 2019-04-29 21:09 UTC (permalink / raw)
  To: Alan Stern
  Cc: syzbot, andreyknvl, gregkh, linux-kernel, linux-usb, rafael,
	syzkaller-bugs

On Mon, Apr 29, 2019 at 04:07:04PM -0400, Alan Stern wrote:
> On Mon, 29 Apr 2019, syzbot wrote:
> 
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> > 
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> > Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> > 
> > CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> > Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0xe8/0x16e lib/dump_stack.c:113
> >   print_address_description+0x6c/0x236 mm/kasan/report.c:187
> >   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
> >   hex_string+0x418/0x4b0 lib/vsprintf.c:975
> >   pointer+0x460/0x910 lib/vsprintf.c:1985
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   pointer+0x60b/0x910 lib/vsprintf.c:2038
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
> >   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
> >   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
> >   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
> >   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
> >   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
> >   _dev_info+0xdc/0x10e drivers/base/core.c:3254
> >   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
> 
> Accessing beyond the end of the descriptor.
> 
> #syz test: https://github.com/google/kasan.git usb-fuzzer
> 
> --- a/drivers/video/fbdev/udlfb.c
> +++ b/drivers/video/fbdev/udlfb.c
> @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
>  	char *buf;
>  	char *desc_end;
>  	int total_len;
> +	int width;
>  
>  	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
>  	if (!buf)
> @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
>  	}
>  
>  	if (total_len > 5) {
> +		width = min(total_len, 11);
>  		dev_info(&intf->dev,
> -			 "vendor descriptor length: %d data: %11ph\n",
> -			 total_len, desc);
> +			 "vendor descriptor length: %d data: %*ph\n",
> +			 total_len, width, desc);
>  
>  		if ((desc[0] != total_len) || /* descriptor length */
>  		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
> 
> 

Why not write just:

                dev_info(&intf->dev,
                         "vendor descriptor length: %d data: %*ph\n",
                         total_len, min(total_len, 11), desc);

Also, aren't there more out-of-bounds reads in the code just after?  It only
checks for at least 1 byte available, but then it reads up to 7 bytes:

		while (desc < desc_end) {
			u8 length;
			u16 key;

			key = *desc++;
			key |= (u16)*desc++ << 8;
			length = *desc++;

			switch (key) {
			case 0x0200: { /* max_area */
				u32 max_area = *desc++;
				max_area |= (u32)*desc++ << 8;
				max_area |= (u32)*desc++ << 16;
				max_area |= (u32)*desc++ << 24;
				dev_warn(&intf->dev,
					 "DL chip limited to %d pixel modes\n",
					 max_area);
				dlfb->sku_pixel_limit = max_area;
				break;
			}
			default:
				break;
			}
			desc += length;
		}


Also I couldn't help but notice it's also using 'char' rather than 'u8',
so bytes >= 0x80 are read incorrectly as they're sign extended...

- Eric

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-29 21:09   ` Eric Biggers
@ 2019-04-29 21:09     ` Eric Biggers
  2019-04-30 14:13     ` Alan Stern
  1 sibling, 0 replies; 12+ messages in thread
From: Eric Biggers @ 2019-04-29 21:09 UTC (permalink / raw)
  To: Alan Stern
  Cc: syzbot, andreyknvl, gregkh, linux-kernel, linux-usb, rafael,
	syzkaller-bugs

On Mon, Apr 29, 2019 at 04:07:04PM -0400, Alan Stern wrote:
> On Mon, 29 Apr 2019, syzbot wrote:
> 
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a9fefd18c7b240f19c54@syzkaller.appspotmail.com
> > 
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> > Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
> > 
> > CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> > Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > Call Trace:
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0xe8/0x16e lib/dump_stack.c:113
> >   print_address_description+0x6c/0x236 mm/kasan/report.c:187
> >   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
> >   hex_string+0x418/0x4b0 lib/vsprintf.c:975
> >   pointer+0x460/0x910 lib/vsprintf.c:1985
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   pointer+0x60b/0x910 lib/vsprintf.c:2038
> >   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
> >   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
> >   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
> >   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
> >   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
> >   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
> >   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
> >   _dev_info+0xdc/0x10e drivers/base/core.c:3254
> >   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
> 
> Accessing beyond the end of the descriptor.
> 
> #syz test: https://github.com/google/kasan.git usb-fuzzer
> 
> --- a/drivers/video/fbdev/udlfb.c
> +++ b/drivers/video/fbdev/udlfb.c
> @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
>  	char *buf;
>  	char *desc_end;
>  	int total_len;
> +	int width;
>  
>  	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
>  	if (!buf)
> @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
>  	}
>  
>  	if (total_len > 5) {
> +		width = min(total_len, 11);
>  		dev_info(&intf->dev,
> -			 "vendor descriptor length: %d data: %11ph\n",
> -			 total_len, desc);
> +			 "vendor descriptor length: %d data: %*ph\n",
> +			 total_len, width, desc);
>  
>  		if ((desc[0] != total_len) || /* descriptor length */
>  		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
> 
> 

Why not write just:

                dev_info(&intf->dev,
                         "vendor descriptor length: %d data: %*ph\n",
                         total_len, min(total_len, 11), desc);

Also, aren't there more out-of-bounds reads in the code just after?  It only
checks for at least 1 byte available, but then it reads up to 7 bytes:

		while (desc < desc_end) {
			u8 length;
			u16 key;

			key = *desc++;
			key |= (u16)*desc++ << 8;
			length = *desc++;

			switch (key) {
			case 0x0200: { /* max_area */
				u32 max_area = *desc++;
				max_area |= (u32)*desc++ << 8;
				max_area |= (u32)*desc++ << 16;
				max_area |= (u32)*desc++ << 24;
				dev_warn(&intf->dev,
					 "DL chip limited to %d pixel modes\n",
					 max_area);
				dlfb->sku_pixel_limit = max_area;
				break;
			}
			default:
				break;
			}
			desc += length;
		}


Also I couldn't help but notice it's also using 'char' rather than 'u8',
so bytes >= 0x80 are read incorrectly as they're sign extended...

- Eric

^ permalink raw reply	[flat|nested] 12+ messages in thread

* KASAN: slab-out-of-bounds Read in hex_string
@ 2019-04-30 14:13     ` Alan Stern
  2019-04-30 14:13       ` Alan Stern
  2019-08-13 12:55       ` Andrey Konovalov
  0 siblings, 2 replies; 12+ messages in thread
From: Alan Stern @ 2019-04-30 14:13 UTC (permalink / raw)
  To: Eric Biggers
  Cc: syzbot, andreyknvl, gregkh, linux-kernel, linux-usb, rafael,
	syzkaller-bugs

On Mon, 29 Apr 2019, Eric Biggers wrote:

> On Mon, Apr 29, 2019 at 04:07:04PM -0400, Alan Stern wrote:

> > Accessing beyond the end of the descriptor.
> > 
> > #syz test: https://github.com/google/kasan.git usb-fuzzer
> > 
> > --- a/drivers/video/fbdev/udlfb.c
> > +++ b/drivers/video/fbdev/udlfb.c
> > @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
> >  	char *buf;
> >  	char *desc_end;
> >  	int total_len;
> > +	int width;
> >  
> >  	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
> >  	if (!buf)
> > @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
> >  	}
> >  
> >  	if (total_len > 5) {
> > +		width = min(total_len, 11);
> >  		dev_info(&intf->dev,
> > -			 "vendor descriptor length: %d data: %11ph\n",
> > -			 total_len, desc);
> > +			 "vendor descriptor length: %d data: %*ph\n",
> > +			 total_len, width, desc);
> >  
> >  		if ((desc[0] != total_len) || /* descriptor length */
> >  		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
> > 
> > 
> 
> Why not write just:
> 
>                 dev_info(&intf->dev,
>                          "vendor descriptor length: %d data: %*ph\n",
>                          total_len, min(total_len, 11), desc);

I did consider doing that.  In the end I decided adding an extra
temporary variable made the code a little more readable.  (For some 
reason, extra recursion -- a function call embedded in a function 
argument -- seems to demand more mental effort than an extra 
temporary.  Maybe my brain is just getting old...)

> Also, aren't there more out-of-bounds reads in the code just after?  It only
> checks for at least 1 byte available, but then it reads up to 7 bytes:
> 
> 		while (desc < desc_end) {
> 			u8 length;
> 			u16 key;
> 
> 			key = *desc++;
> 			key |= (u16)*desc++ << 8;
> 			length = *desc++;
> 
> 			switch (key) {
> 			case 0x0200: { /* max_area */
> 				u32 max_area = *desc++;
> 				max_area |= (u32)*desc++ << 8;
> 				max_area |= (u32)*desc++ << 16;
> 				max_area |= (u32)*desc++ << 24;
> 				dev_warn(&intf->dev,
> 					 "DL chip limited to %d pixel modes\n",
> 					 max_area);
> 				dlfb->sku_pixel_limit = max_area;
> 				break;
> 			}
> 			default:
> 				break;
> 			}
> 			desc += length;
> 		}

Quite right.  Please feel free to submit a patch fixing all these 
problems.

> Also I couldn't help but notice it's also using 'char' rather than 'u8',
> so bytes >= 0x80 are read incorrectly as they're sign extended...

As I recall, the C standard doesn't specify whether char is signed or
unsigned; it can vary with the implementation.  However you are
certainly correct that to ensure there is no sign extension, the code
should use unsigned char or u8.

Alan Stern

^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-30 14:13     ` Alan Stern
@ 2019-04-30 14:13       ` Alan Stern
  2019-08-13 12:55       ` Andrey Konovalov
  1 sibling, 0 replies; 12+ messages in thread
From: Alan Stern @ 2019-04-30 14:13 UTC (permalink / raw)
  To: Eric Biggers
  Cc: syzbot, andreyknvl, gregkh, linux-kernel, linux-usb, rafael,
	syzkaller-bugs

On Mon, 29 Apr 2019, Eric Biggers wrote:

> On Mon, Apr 29, 2019 at 04:07:04PM -0400, Alan Stern wrote:

> > Accessing beyond the end of the descriptor.
> > 
> > #syz test: https://github.com/google/kasan.git usb-fuzzer
> > 
> > --- a/drivers/video/fbdev/udlfb.c
> > +++ b/drivers/video/fbdev/udlfb.c
> > @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
> >  	char *buf;
> >  	char *desc_end;
> >  	int total_len;
> > +	int width;
> >  
> >  	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
> >  	if (!buf)
> > @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
> >  	}
> >  
> >  	if (total_len > 5) {
> > +		width = min(total_len, 11);
> >  		dev_info(&intf->dev,
> > -			 "vendor descriptor length: %d data: %11ph\n",
> > -			 total_len, desc);
> > +			 "vendor descriptor length: %d data: %*ph\n",
> > +			 total_len, width, desc);
> >  
> >  		if ((desc[0] != total_len) || /* descriptor length */
> >  		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
> > 
> > 
> 
> Why not write just:
> 
>                 dev_info(&intf->dev,
>                          "vendor descriptor length: %d data: %*ph\n",
>                          total_len, min(total_len, 11), desc);

I did consider doing that.  In the end I decided adding an extra
temporary variable made the code a little more readable.  (For some 
reason, extra recursion -- a function call embedded in a function 
argument -- seems to demand more mental effort than an extra 
temporary.  Maybe my brain is just getting old...)

> Also, aren't there more out-of-bounds reads in the code just after?  It only
> checks for at least 1 byte available, but then it reads up to 7 bytes:
> 
> 		while (desc < desc_end) {
> 			u8 length;
> 			u16 key;
> 
> 			key = *desc++;
> 			key |= (u16)*desc++ << 8;
> 			length = *desc++;
> 
> 			switch (key) {
> 			case 0x0200: { /* max_area */
> 				u32 max_area = *desc++;
> 				max_area |= (u32)*desc++ << 8;
> 				max_area |= (u32)*desc++ << 16;
> 				max_area |= (u32)*desc++ << 24;
> 				dev_warn(&intf->dev,
> 					 "DL chip limited to %d pixel modes\n",
> 					 max_area);
> 				dlfb->sku_pixel_limit = max_area;
> 				break;
> 			}
> 			default:
> 				break;
> 			}
> 			desc += length;
> 		}

Quite right.  Please feel free to submit a patch fixing all these 
problems.

> Also I couldn't help but notice it's also using 'char' rather than 'u8',
> so bytes >= 0x80 are read incorrectly as they're sign extended...

As I recall, the C standard doesn't specify whether char is signed or
unsigned; it can vary with the implementation.  However you are
certainly correct that to ensure there is no sign extension, the code
should use unsigned char or u8.

Alan Stern


^ permalink raw reply	[flat|nested] 12+ messages in thread

* Re: KASAN: slab-out-of-bounds Read in hex_string
  2019-04-30 14:13     ` Alan Stern
  2019-04-30 14:13       ` Alan Stern
@ 2019-08-13 12:55       ` Andrey Konovalov
  1 sibling, 0 replies; 12+ messages in thread
From: Andrey Konovalov @ 2019-08-13 12:55 UTC (permalink / raw)
  To: Alan Stern, Eric Biggers
  Cc: syzbot, Greg Kroah-Hartman, LKML, USB list, rafael, syzkaller-bugs

On Tue, Apr 30, 2019 at 4:13 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Mon, 29 Apr 2019, Eric Biggers wrote:
>
> > On Mon, Apr 29, 2019 at 04:07:04PM -0400, Alan Stern wrote:
>
> > > Accessing beyond the end of the descriptor.
> > >
> > > #syz test: https://github.com/google/kasan.git usb-fuzzer
> > >
> > > --- a/drivers/video/fbdev/udlfb.c
> > > +++ b/drivers/video/fbdev/udlfb.c
> > > @@ -1511,6 +1511,7 @@ static int dlfb_parse_vendor_descriptor(
> > >     char *buf;
> > >     char *desc_end;
> > >     int total_len;
> > > +   int width;
> > >
> > >     buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
> > >     if (!buf)
> > > @@ -1529,9 +1530,10 @@ static int dlfb_parse_vendor_descriptor(
> > >     }
> > >
> > >     if (total_len > 5) {
> > > +           width = min(total_len, 11);
> > >             dev_info(&intf->dev,
> > > -                    "vendor descriptor length: %d data: %11ph\n",
> > > -                    total_len, desc);
> > > +                    "vendor descriptor length: %d data: %*ph\n",
> > > +                    total_len, width, desc);
> > >
> > >             if ((desc[0] != total_len) || /* descriptor length */
> > >                 (desc[1] != 0x5f) ||   /* vendor descriptor type */
> > >
> > >
> >
> > Why not write just:
> >
> >                 dev_info(&intf->dev,
> >                          "vendor descriptor length: %d data: %*ph\n",
> >                          total_len, min(total_len, 11), desc);
>
> I did consider doing that.  In the end I decided adding an extra
> temporary variable made the code a little more readable.  (For some
> reason, extra recursion -- a function call embedded in a function
> argument -- seems to demand more mental effort than an extra
> temporary.  Maybe my brain is just getting old...)
>
> > Also, aren't there more out-of-bounds reads in the code just after?  It only
> > checks for at least 1 byte available, but then it reads up to 7 bytes:
> >
> >               while (desc < desc_end) {
> >                       u8 length;
> >                       u16 key;
> >
> >                       key = *desc++;
> >                       key |= (u16)*desc++ << 8;
> >                       length = *desc++;
> >
> >                       switch (key) {
> >                       case 0x0200: { /* max_area */
> >                               u32 max_area = *desc++;
> >                               max_area |= (u32)*desc++ << 8;
> >                               max_area |= (u32)*desc++ << 16;
> >                               max_area |= (u32)*desc++ << 24;
> >                               dev_warn(&intf->dev,
> >                                        "DL chip limited to %d pixel modes\n",
> >                                        max_area);
> >                               dlfb->sku_pixel_limit = max_area;
> >                               break;
> >                       }
> >                       default:
> >                               break;
> >                       }
> >                       desc += length;
> >               }
>
> Quite right.  Please feel free to submit a patch fixing all these
> problems.
>
> > Also I couldn't help but notice it's also using 'char' rather than 'u8',
> > so bytes >= 0x80 are read incorrectly as they're sign extended...
>
> As I recall, the C standard doesn't specify whether char is signed or
> unsigned; it can vary with the implementation.  However you are
> certainly correct that to ensure there is no sign extension, the code
> should use unsigned char or u8.

Hi Alan and Eric,

Have any of this fixes been submitted anywhere? This bug is still open
on syzbot.

Thanks!

^ permalink raw reply	[flat|nested] 12+ messages in thread

end of thread, back to index

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-04-29 12:06 KASAN: slab-out-of-bounds Read in hex_string syzbot
2019-04-29 20:07 ` Alan Stern
2019-04-29 20:07   ` Alan Stern
2019-04-29 20:24   ` Andrey Konovalov
2019-04-29 20:24     ` Andrey Konovalov
2019-04-29 20:52   ` syzbot
2019-04-29 20:52     ` syzbot
2019-04-29 21:09   ` Eric Biggers
2019-04-29 21:09     ` Eric Biggers
2019-04-30 14:13     ` Alan Stern
2019-04-30 14:13       ` Alan Stern
2019-08-13 12:55       ` Andrey Konovalov

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