[Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Dick]

Hi All,

I'm trying to add a SDP_ATTR_HID_DESCRIPTOR_LIST attribute to a SDP record. I've
followed the (removed) "add_hid_keyb" implementation from an old sdptool.c but
it segfaults!
Is there a more correct example for adding data like a descriptor list to sdp?

TIA
Dick


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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Dick]

Marcel Holtmann <marcel <at> holtmann.org> writes:
> nothing has been removed from sdptool.c and the code works perfectly
> fine.

ah now I see, add_hid_keyb isn't removed but added recently, and my bluez-utils
are really outdated...

thanks for your reply!


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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Marcel Holtmann]

Hi Dick,

> I'm trying to add a SDP_ATTR_HID_DESCRIPTOR_LIST attribute to a SDP record. I've
> followed the (removed) "add_hid_keyb" implementation from an old sdptool.c but
> it segfaults!
> Is there a more correct example for adding data like a descriptor list to sdp?

nothing has been removed from sdptool.c and the code works perfectly
fine.

Regards

Marcel



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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Dick]

Oh boy I've found the segfault :-)

My HID descriptor is too large to fit in SDP_SEQ_PDUFORM_SIZE
... I almost wouldn't dare to ask but ... 
Could it please be increased from 128 to something larger or equal to 168?

It would also be nice to have some range checking ;-)

TIA

Dick


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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Dick]

Marcel Holtmann <marcel <at> holtmann.org> writes:
> what are you talking about. I have no idea and it would be better if you
> send me an example on how to reproduce this segmentation fault.

Hi Marcel,

try the following patch on bluez-utils-3.4:
--- tools/sdptool.c      2006-06-17 16:31:37.000000000 +0200
+++ tools/sdptool.c      2006-09-03 21:54:54.000000000 +0200
@@ -2139,6 +2139,21 @@
                0x75, 0x01,
                0x95, 0x04,
                0x81, 0x01,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
+               0x0, 0x0,
                0xc0         // end tag
        };

(this patch adds 30 zero's to hid_report so it is >128)

and see:
$ sdptool add keyb
Segmentation fault

the following patch on bluez-utils:
$ sed -i -e 's/\(#define SDP_SEQ_PDUFORM_SIZE\) 128/\1 256/' ${S}/src/sdp.c

fixes the problem for me... (increasing the PDUFORM_SIZE)

So my questions are:
- could you increase the SDP_SEQ_PDUFORM_SIZE
- it would be nice to have some range checking, it's very confusing because the
segfault occures in sdp_record_register and not in
sdp_attr_add()/sdp_data_alloc()/sdp_seql_alloc()

greetings,
Dick


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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Marcel Holtmann]

Hi Dick,

> Oh boy I've found the segfault :-)
> 
> My HID descriptor is too large to fit in SDP_SEQ_PDUFORM_SIZE
> ... I almost wouldn't dare to ask but ... 
> Could it please be increased from 128 to something larger or equal to 168?
> 
> It would also be nice to have some range checking ;-)

what are you talking about. I have no idea and it would be better if you
send me an example on how to reproduce this segmentation fault.

Regards

Marcel



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Re: [Bluez-users] adding a SDP attribute HID_DESCRIPTOR_LIST

[Marcel Holtmann]

Hi Dick,

> > what are you talking about. I have no idea and it would be better if you
> > send me an example on how to reproduce this segmentation fault.
> 
> try the following patch on bluez-utils-3.4:
> --- tools/sdptool.c      2006-06-17 16:31:37.000000000 +0200
> +++ tools/sdptool.c      2006-09-03 21:54:54.000000000 +0200
> @@ -2139,6 +2139,21 @@
>                 0x75, 0x01,
>                 0x95, 0x04,
>                 0x81, 0x01,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
> +               0x0, 0x0,
>                 0xc0         // end tag
>         };
> 
> (this patch adds 30 zero's to hid_report so it is >128)

the used buffer is from the stack and we end up overwriting the stack.

> and see:
> $ sdptool add keyb
> Segmentation fault
> 
> the following patch on bluez-utils:
> $ sed -i -e 's/\(#define SDP_SEQ_PDUFORM_SIZE\) 128/\1 256/' ${S}/src/sdp.c
> 
> fixes the problem for me... (increasing the PDUFORM_SIZE)
> 
> So my questions are:
> - could you increase the SDP_SEQ_PDUFORM_SIZE

I removed the constant completely and increased the buffer to 256 byte
for now.

> - it would be nice to have some range checking, it's very confusing because the
> segfault occures in sdp_record_register and not in
> sdp_attr_add()/sdp_data_alloc()/sdp_seql_alloc()

The problem is actually in sdp_append_to_pdu() and this needs fixing.
Feel free to propose a patch. And it would be better to not use stack
memory for this.

Regards

Marcel



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