| Message ID | 20250401214703.7809-1-qasdev00@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] HID: wacom: fix shift OOB in kfifo allocation for zero pktlen | expand |
On Wed, Apr 02, 2025 at 10:03:25AM +0200, Markus Elfring wrote: > … > > To fix this, we should handle cases where wacom_compute_pktlen() > > results in 0. > > See also once more: > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.14#n94 > > Regards, > Markus > Hi, This is the semi-friendly patch-bot of Greg Kroah-Hartman. Markus, you seem to have sent a nonsensical or otherwise pointless review comment to a patch submission on a Linux kernel developer mailing list. I strongly suggest that you not do this anymore. Please do not bother developers who are actively working to produce patches and features with comments that, in the end, are a waste of time. Patch submitter, please ignore Markus's suggestion; you do not need to follow it at all. The person/bot/AI that sent it is being ignored by almost all Linux kernel maintainers for having a persistent pattern of behavior of producing distracting and pointless commentary, and inability to adapt to feedback. Please feel free to also ignore emails from them. thanks, greg k-h's patch email bot
diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index 97393a3083ca..9b2f3dbca467 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -2361,6 +2361,8 @@ static int wacom_parse_and_register(struct wacom *wacom, bool wireless) unsigned int connect_mask = HID_CONNECT_HIDRAW; features->pktlen = wacom_compute_pktlen(hdev); + if (!features->pktlen) + return -ENODEV; if (!devres_open_group(&hdev->dev, wacom, GFP_KERNEL)) return -ENOMEM;
During wacom_parse_and_register() the code calls wacom_devm_kfifo_alloc to allocate a fifo. During this operation it passes kfifo_alloc a fifo_size of 0. Kfifo attempts to round the size passed to it to the next power of 2 via roundup_pow_of_two (queue-type data structures do this to maintain efficiency of operations). However during this phase a problem arises when the roundup_pow_of_two() function utilises a shift exponent of fls_long(n-1), where n is the fifo_size. Since n is 0 in this case and n is also an unsigned long, doing n-1 causes unsigned integer wrap-around to occur making the fifo_size 4294967295. So the code effectively does fls_long(4294967295) which results in 64. Returning back to roundup_pow_of_two(), the code utilises a shift exponent of 64. When a shift exponent of 64 is used on a 64-bit type such as 1UL it results in a shift-out-of-bounds. The root cause of the issue seems to stem from insufficient validation of wacom_compute_pktlen(), since in this case the fifo_size comes from wacom_wac->features.pktlen. During wacom_parse_and_register() the wacom_compute_pktlen() function sets the pktlen as 0. To fix this, we should handle cases where wacom_compute_pktlen() results in 0. Reported-by: syzbot <syzbot+d5204cbbdd921f1f7cad@syzkaller.appspotmail.com> Closes: https://syzkaller.appspot.com/bug?extid=d5204cbbdd921f1f7cad Fixes: 5e013ad20689 ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit") Tested-by: Qasim Ijaz <qasdev00@gmail.com> Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com> Cc: stable@vger.kernel.org Signed-off-by: Qasim Ijaz <qasdev00@gmail.com> --- v2: - Added Fixes tag as suggested by Jason Gerecke drivers/hid/wacom_sys.c | 2 ++ 1 file changed, 2 insertions(+)