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* BUG: bad usercopy in ld_usb_read
@ 2019-08-08 12:38 syzbot
  2019-08-08 12:46 ` Greg KH
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: syzbot @ 2019-08-08 12:38 UTC (permalink / raw)
  To: akpm, andreyknvl, cai, gregkh, keescook, linux-kernel, linux-mm,
	linux-usb, syzkaller-bugs, tglx

Hello,

syzbot found the following crash on:

HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com

ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
usercopy: Kernel memory exposure attempt detected from SLUB  
object 'kmalloc-2k' (offset 8, size 65062)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:98!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 15185 Comm: syz-executor.2 Not tainted 5.3.0-rc2+ #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881ccb3fc38 EFLAGS: 00010286
RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  __check_heap_object+0xdd/0x110 mm/slub.c:3914
  check_heap_object mm/usercopy.c:234 [inline]
  __check_object_size mm/usercopy.c:280 [inline]
  __check_object_size+0x32d/0x39b mm/usercopy.c:250
  check_object_size include/linux/thread_info.h:119 [inline]
  check_copy_size include/linux/thread_info.h:150 [inline]
  copy_to_user include/linux/uaccess.h:151 [inline]
  ld_usb_read+0x304/0x780 drivers/usb/misc/ldusb.c:495
  __vfs_read+0x76/0x100 fs/read_write.c:425
  vfs_read+0x1ea/0x430 fs/read_write.c:461
  ksys_read+0x1e8/0x250 fs/read_write.c:587
  do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff6daf90c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 000000000000fe26 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff6daf916d4
R13: 00000000004c6c73 R14: 00000000004dbee8 R15: 00000000ffffffff
Modules linked in:
---[ end trace 4fe8dba032d24ceb ]---
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881ccb3fc38 EFLAGS: 00010286
RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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.

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-08 12:38 BUG: bad usercopy in ld_usb_read syzbot
@ 2019-08-08 12:46 ` Greg KH
  2019-08-08 23:06   ` Kees Cook
  2019-08-10 18:15 ` syzbot
  2019-08-12 12:06 ` Andrey Konovalov
  2 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2019-08-08 12:46 UTC (permalink / raw)
  To: syzbot, Michael Hund
  Cc: akpm, andreyknvl, cai, keescook, linux-kernel, linux-mm,
	linux-usb, syzkaller-bugs, tglx

On Thu, Aug 08, 2019 at 05:38:06AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
> 
> ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped

That's a funny number :)

Nice overflow found, I see you are now starting to fuzz the char device
nodes of usb drivers...

Michael, care to fix this up?

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-08 12:46 ` Greg KH
@ 2019-08-08 23:06   ` Kees Cook
  2019-08-09  8:55     ` Greg KH
  0 siblings, 1 reply; 8+ messages in thread
From: Kees Cook @ 2019-08-08 23:06 UTC (permalink / raw)
  To: Greg KH
  Cc: syzbot, Michael Hund, akpm, andreyknvl, cai, linux-kernel,
	linux-mm, linux-usb, syzkaller-bugs, tglx

On Thu, Aug 08, 2019 at 02:46:54PM +0200, Greg KH wrote:
> On Thu, Aug 08, 2019 at 05:38:06AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> > dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > 
> > Unfortunately, I don't have any reproducer for this crash yet.
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
> > 
> > ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
> 
> That's a funny number :)
> 
> Nice overflow found, I see you are now starting to fuzz the char device
> nodes of usb drivers...
> 
> Michael, care to fix this up?

This looks like the length in the read-from-device buffer is unchecked:

        /* actual_buffer contains actual_length + interrupt_in_buffer */
        actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
        bytes_to_read = min(count, *actual_buffer);
        if (bytes_to_read < *actual_buffer)
                dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
                         *actual_buffer-bytes_to_read);

        /* copy one interrupt_in_buffer from ring_buffer into userspace */
        if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
                retval = -EFAULT;
                goto unlock_exit;
        }

I assume what's stored at actual_buffer is bogus and needs validation
somewhere before it's actually used. (If not here, maybe where ever the
write into the buffer originally happens?)

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-08 23:06   ` Kees Cook
@ 2019-08-09  8:55     ` Greg KH
  2019-08-09 15:13       ` Alan Stern
  0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2019-08-09  8:55 UTC (permalink / raw)
  To: Kees Cook
  Cc: syzbot, Michael Hund, akpm, andreyknvl, cai, linux-kernel,
	linux-mm, linux-usb, syzkaller-bugs, tglx

On Thu, Aug 08, 2019 at 04:06:32PM -0700, Kees Cook wrote:
> On Thu, Aug 08, 2019 at 02:46:54PM +0200, Greg KH wrote:
> > On Thu, Aug 08, 2019 at 05:38:06AM -0700, syzbot wrote:
> > > Hello,
> > > 
> > > syzbot found the following crash on:
> > > 
> > > HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> > > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> > > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > > 
> > > Unfortunately, I don't have any reproducer for this crash yet.
> > > 
> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > > Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
> > > 
> > > ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
> > 
> > That's a funny number :)
> > 
> > Nice overflow found, I see you are now starting to fuzz the char device
> > nodes of usb drivers...
> > 
> > Michael, care to fix this up?
> 
> This looks like the length in the read-from-device buffer is unchecked:
> 
>         /* actual_buffer contains actual_length + interrupt_in_buffer */
>         actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
>         bytes_to_read = min(count, *actual_buffer);
>         if (bytes_to_read < *actual_buffer)
>                 dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
>                          *actual_buffer-bytes_to_read);
> 
>         /* copy one interrupt_in_buffer from ring_buffer into userspace */
>         if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
>                 retval = -EFAULT;
>                 goto unlock_exit;
>         }
> 
> I assume what's stored at actual_buffer is bogus and needs validation
> somewhere before it's actually used. (If not here, maybe where ever the
> write into the buffer originally happens?)

I think it should be verified here, as that's when it is parsed.  The
data is written to the buffer in ld_usb_interrupt_in_callback() but it
does not "know" how to parse it at that location.

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-09  8:55     ` Greg KH
@ 2019-08-09 15:13       ` Alan Stern
  2019-08-10 18:23         ` Kees Cook
  0 siblings, 1 reply; 8+ messages in thread
From: Alan Stern @ 2019-08-09 15:13 UTC (permalink / raw)
  To: Greg KH
  Cc: Kees Cook, syzbot, Michael Hund, akpm, andreyknvl, cai,
	linux-kernel, linux-mm, linux-usb, syzkaller-bugs, tglx

On Fri, 9 Aug 2019, Greg KH wrote:

> On Thu, Aug 08, 2019 at 04:06:32PM -0700, Kees Cook wrote:
> > On Thu, Aug 08, 2019 at 02:46:54PM +0200, Greg KH wrote:
> > > On Thu, Aug 08, 2019 at 05:38:06AM -0700, syzbot wrote:
> > > > Hello,
> > > > 
> > > > syzbot found the following crash on:
> > > > 
> > > > HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> > > > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> > > > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > > > 
> > > > Unfortunately, I don't have any reproducer for this crash yet.
> > > > 
> > > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > > > Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
> > > > 
> > > > ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
> > > 
> > > That's a funny number :)
> > > 
> > > Nice overflow found, I see you are now starting to fuzz the char device
> > > nodes of usb drivers...
> > > 
> > > Michael, care to fix this up?
> > 
> > This looks like the length in the read-from-device buffer is unchecked:
> > 
> >         /* actual_buffer contains actual_length + interrupt_in_buffer */
> >         actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
> >         bytes_to_read = min(count, *actual_buffer);
> >         if (bytes_to_read < *actual_buffer)
> >                 dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
> >                          *actual_buffer-bytes_to_read);
> > 
> >         /* copy one interrupt_in_buffer from ring_buffer into userspace */
> >         if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
> >                 retval = -EFAULT;
> >                 goto unlock_exit;
> >         }
> > 
> > I assume what's stored at actual_buffer is bogus and needs validation
> > somewhere before it's actually used. (If not here, maybe where ever the
> > write into the buffer originally happens?)
> 
> I think it should be verified here, as that's when it is parsed.  The
> data is written to the buffer in ld_usb_interrupt_in_callback() but it
> does not "know" how to parse it at that location.

I looked at this bug report, and it is very puzzling.

Yes, the value stored in *actual_buffer is written in
ld_usb_interrupt_in_callback(), but the value is simply
urb->actual_length and therefore does not need any validation.  The 
URB's transfer_buffer_length is taken from 
dev->interrupt_in_endpoint_size, which comes from usb_endpoint_maxp() 
and therefore cannot be larger than 2048.

(On the other hand, actual_buffer might not be aligned on a 32-bit 
address.  For x86, of course, this doesn't matter, but it can affect 
other architectures.)

Furthermore, the computation leading to the dev_warn() involves only
size_t types and therefore is carried out entirely using unsigned
arithmetic.  The warning's format string uses %zd instead of %zu;  
that's why the number showed up as negative but doesn't explain why it
looks so funny.

In fact, I don't see why any of the computations here should overflow
or wrap around, or even give rise to a negative value.  If syzbot had a
reproducer we could get more debugging output -- but it doesn't.

Alan Stern


^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-08 12:38 BUG: bad usercopy in ld_usb_read syzbot
  2019-08-08 12:46 ` Greg KH
@ 2019-08-10 18:15 ` syzbot
  2019-08-12 12:06 ` Andrey Konovalov
  2 siblings, 0 replies; 8+ messages in thread
From: syzbot @ 2019-08-10 18:15 UTC (permalink / raw)
  To: akpm, allison, andreyknvl, cai, gregkh, keescook, linux-kernel,
	linux-mm, linux-usb, mhund, stern, syzkaller-bugs, tglx

syzbot has found a reproducer for the following crash on:

HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=17cf0b16600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=151bab16600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=148f8cd2600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com

ldusb 4-1:0.28: Read buffer overflow, -3222596215958809898 bytes dropped
usercopy: Kernel memory exposure attempt detected from process stack  
(offset 0, size 2147479552)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:98!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 1 PID: 2023 Comm: syz-executor861 Not tainted 5.3.0-rc2+ #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881cbda7c40 EFLAGS: 00010282
RAX: 0000000000000061 RBX: ffffffff85cdf100 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed10397b4f7a
RBP: ffffffff85cdf2c0 R08: 0000000000000061 R09: fffffbfff11acda1
R10: fffffbfff11acda0 R11: ffffffff88d66d07 R12: ffffffff85cdf4e0
R13: ffffffff85cdf100 R14: 000000007ffff000 R15: ffffffff85cdf100
FS:  00007f10bb76a700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7135a49000 CR3: 00000001d20e8000 CR4: 00000000001406e0
Call Trace:
  __check_object_size mm/usercopy.c:276 [inline]
  __check_object_size.cold+0x91/0xba mm/usercopy.c:250
  check_object_size include/linux/thread_info.h:119 [inline]
  check_copy_size include/linux/thread_info.h:150 [inline]
  copy_to_user include/linux/uaccess.h:151 [inline]
  ld_usb_read+0x304/0x780 drivers/usb/misc/ldusb.c:495
  __vfs_read+0x76/0x100 fs/read_write.c:425
  vfs_read+0x1ea/0x430 fs/read_write.c:461
  ksys_read+0x1e8/0x250 fs/read_write.c:587
  do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446e19
Code: e8 ec e7 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 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 0f 83 3b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f10bb769d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 0000000000446e19
RDX: 00000000ffffffbc RSI: 0000000020000040 RDI: 0000000000000004
RBP: 00000000006dbc30 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000000f R11: 0000000000000246 R12: 00000000006dbc3c
R13: 0001002402090100 R14: 000048c920200f11 R15: 08983baa00000112
Modules linked in:
---[ end trace 93f3613883c53c00 ]---
RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0  
f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7  
d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
RSP: 0018:ffff8881cbda7c40 EFLAGS: 00010282
RAX: 0000000000000061 RBX: ffffffff85cdf100 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed10397b4f7a
RBP: ffffffff85cdf2c0 R08: 0000000000000061 R09: fffffbfff11acda1
R10: fffffbfff11acda0 R11: ffffffff88d66d07 R12: ffffffff85cdf4e0
R13: ffffffff85cdf100 R14: 000000007ffff000 R15: ffffffff85cdf100
FS:  00007f10bb76a700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7135a49000 CR3: 00000001d20e8000 CR4: 00000000001406e0


^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-09 15:13       ` Alan Stern
@ 2019-08-10 18:23         ` Kees Cook
  0 siblings, 0 replies; 8+ messages in thread
From: Kees Cook @ 2019-08-10 18:23 UTC (permalink / raw)
  To: Alan Stern
  Cc: Greg KH, syzbot, Michael Hund, akpm, andreyknvl, cai,
	linux-kernel, linux-mm, linux-usb, syzkaller-bugs, tglx

On Fri, Aug 09, 2019 at 11:13:00AM -0400, Alan Stern wrote:
> In fact, I don't see why any of the computations here should overflow
> or wrap around, or even give rise to a negative value.  If syzbot had a
> reproducer we could get more debugging output -- but it doesn't.

Yeah, this is odd. The only thing I could see here with more study was
that ring_tail is used/updated outside of the rbsl lock in
ld_usb_read(). I couldn't convince myself there wasn't a race against
the interrupt, but I also couldn't think of a way it could break...

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: BUG: bad usercopy in ld_usb_read
  2019-08-08 12:38 BUG: bad usercopy in ld_usb_read syzbot
  2019-08-08 12:46 ` Greg KH
  2019-08-10 18:15 ` syzbot
@ 2019-08-12 12:06 ` Andrey Konovalov
  2 siblings, 0 replies; 8+ messages in thread
From: Andrey Konovalov @ 2019-08-12 12:06 UTC (permalink / raw)
  To: syzbot
  Cc: Andrew Morton, Qian Cai, Greg Kroah-Hartman, Kees Cook, LKML,
	Linux Memory Management List, USB list, syzkaller-bugs,
	Thomas Gleixner

On Thu, Aug 8, 2019 at 2:38 PM syzbot
<syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=13aeaece600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> dashboard link: https://syzkaller.appspot.com/bug?extid=45b2f40f0778cfa7634e
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+45b2f40f0778cfa7634e@syzkaller.appspotmail.com
>
> ldusb 6-1:0.124: Read buffer overflow, -131383996186150 bytes dropped
> usercopy: Kernel memory exposure attempt detected from SLUB
> object 'kmalloc-2k' (offset 8, size 65062)!
> ------------[ cut here ]------------
> kernel BUG at mm/usercopy.c:98!
> invalid opcode: 0000 [#1] SMP KASAN
> CPU: 0 PID: 15185 Comm: syz-executor.2 Not tainted 5.3.0-rc2+ #25
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
> Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0
> f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7
> d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
> RSP: 0018:ffff8881ccb3fc38 EFLAGS: 00010286
> RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
> RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
> R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
> R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
> FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   __check_heap_object+0xdd/0x110 mm/slub.c:3914
>   check_heap_object mm/usercopy.c:234 [inline]
>   __check_object_size mm/usercopy.c:280 [inline]
>   __check_object_size+0x32d/0x39b mm/usercopy.c:250
>   check_object_size include/linux/thread_info.h:119 [inline]
>   check_copy_size include/linux/thread_info.h:150 [inline]
>   copy_to_user include/linux/uaccess.h:151 [inline]
>   ld_usb_read+0x304/0x780 drivers/usb/misc/ldusb.c:495

#syz dup: KASAN: use-after-free Read in ld_usb_release

>   __vfs_read+0x76/0x100 fs/read_write.c:425
>   vfs_read+0x1ea/0x430 fs/read_write.c:461
>   ksys_read+0x1e8/0x250 fs/read_write.c:587
>   do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x459829
> Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ff6daf90c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
> RDX: 000000000000fe26 RSI: 00000000200000c0 RDI: 0000000000000003
> RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff6daf916d4
> R13: 00000000004c6c73 R14: 00000000004dbee8 R15: 00000000ffffffff
> Modules linked in:
> ---[ end trace 4fe8dba032d24ceb ]---
> RIP: 0010:usercopy_abort+0xb9/0xbb mm/usercopy.c:98
> Code: e8 c1 f7 d6 ff 49 89 d9 4d 89 e8 4c 89 e1 41 56 48 89 ee 48 c7 c7 e0
> f3 cd 85 ff 74 24 08 41 57 48 8b 54 24 20 e8 15 98 c1 ff <0f> 0b e8 95 f7
> d6 ff e8 80 9f fd ff 8b 54 24 04 49 89 d8 4c 89 e1
> RSP: 0018:ffff8881ccb3fc38 EFLAGS: 00010286
> RAX: 0000000000000067 RBX: ffffffff86a659d4 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff8128a0fd RDI: ffffed1039967f79
> RBP: ffffffff85cdf2c0 R08: 0000000000000067 R09: fffffbfff11acdaa
> R10: fffffbfff11acda9 R11: ffffffff88d66d4f R12: ffffffff86a696e8
> R13: ffffffff85cdf180 R14: 000000000000fe26 R15: ffffffff85cdf140
> FS:  00007ff6daf91700(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f1de6600000 CR3: 00000001ca554000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
>
> ---
> 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.

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, back to index

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-08 12:38 BUG: bad usercopy in ld_usb_read syzbot
2019-08-08 12:46 ` Greg KH
2019-08-08 23:06   ` Kees Cook
2019-08-09  8:55     ` Greg KH
2019-08-09 15:13       ` Alan Stern
2019-08-10 18:23         ` Kees Cook
2019-08-10 18:15 ` syzbot
2019-08-12 12:06 ` Andrey Konovalov

Linux-USB Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-usb/0 linux-usb/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-usb linux-usb/ https://lore.kernel.org/linux-usb \
		linux-usb@vger.kernel.org linux-usb@archiver.kernel.org
	public-inbox-index linux-usb


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-usb


AGPL code for this site: git clone https://public-inbox.org/ public-inbox