Re: [PATCH] fbdev: udlfb: validate vendor descriptor items

[Helge Deller <deller@gmx.de>]

On 7/18/26 20:26, Helge Deller wrote:
> On 7/6/26 11:30, Pengpeng Hou wrote:
>> dlfb_parse_vendor_descriptor() walks key-length-value items inside the
>> DisplayLink vendor descriptor.
>>
>> Require each item to contain its key, length and declared value bytes
>> before reading item-specific fields such as max_area.
>>
>> Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
>> ---
>>   drivers/video/fbdev/udlfb.c | 22 ++++++++++++++++------
>>   1 file changed, 16 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
>> index fdbb8671a810..e78d6f95c9c5 100644
>> --- a/drivers/video/fbdev/udlfb.c
>> +++ b/drivers/video/fbdev/udlfb.c
>> @@ -1586,19 +1586,29 @@ static int dlfb_parse_vendor_descriptor(struct dlfb_data *dlfb,
>>           desc += 5; /* the fixed header we've already parsed */
>>           while (desc < desc_end) {
>> +            char *value;
>>               u8 length;
>>               u16 key;
>> -            key = *desc++;
>> -            key |= (u16)*desc++ << 8;
>> +            if (desc_end - desc < sizeof(key) + sizeof(length))
>> +                goto unrecognized;
>> +
>> +            key = get_unaligned_le16(desc);
> 
> Is there a reason why you switch to unconditional little-endian reads?
> Is this "vendor descriptor" always little-endian?
> If yes, then your patch is probably correct.
> If not, I think your patch will most likely break big-endian machines.
Please ignore my comments above.
I should have looked more closely.
Your patch is of course correct!

The patch is now added to fbdev git tree.

Thanks!
Helge