On 2/5/20 10:32 AM, Greg Kroah-Hartman wrote:
On Wed, Feb 05, 2020 at 08:12:27AM +0100, peter enderborg wrote:
On 1/14/20 11:00 AM, Greg Kroah-Hartman wrote:
From: Alan Stern stern@rowland.harvard.edu
commit 8ec321e96e056de84022c032ffea253431a83c3c upstream.
The syzbot fuzzer found a slab-out-of-bounds bug in the HID report handler. The bug was caused by a report descriptor which included a field with size 12 bits and count 4899, for a total size of 7349 bytes.
The usbhid driver uses at most a single-page 4-KB buffer for reports. In the test there wasn't any problem about overflowing the buffer, since only one byte was received from the device. Rather, the bug occurred when the HID core tried to extract the data from the report fields, which caused it to try reading data beyond the end of the allocated buffer.
This patch fixes the problem by rejecting any report whose total length exceeds the HID_MAX_BUFFER_SIZE limit (minus one byte to allow for a possible report index). In theory a device could have a report longer than that, but if there was such a thing we wouldn't handle it correctly anyway.
Reported-and-tested-by: syzbot+09ef48aa58261464b621@syzkaller.appspotmail.com Signed-off-by: Alan Stern stern@rowland.harvard.edu CC: stable@vger.kernel.org Signed-off-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/hid/hid-core.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -288,6 +288,12 @@ static int hid_add_field(struct hid_pars offset = report->size; report->size += parser->global.report_size * parser->global.report_count;
- /* Total size check: Allow for possible report index byte */
- if (report->size > (HID_MAX_BUFFER_SIZE - 1) << 3) {
hid_err(parser->device, "report is too long\n");return -1;- }
- if (!parser->local.usage_index) /* Ignore padding fields */ return 0;
This patch breaks Elgato StreamDeck.
Does that mean the device is broken with a too-large of a report?
Yes.
Is it broken in Linus's tree? If so, can you work with the HID developers to fix it there so we can backport the fix to all stable trees?
I cant see that there are any other fixes upon this so I dont think so. I can try.
Jiri is in the loop. I guess he is the "HID developers" ?
thanks,
greg k-h