On Tue, 27 Apr 2021 15:04:29 +0300 Pavel Skripkin <paskripkin@xxxxxxxxx> wrote: > Hi! > > On Tue, 2021-04-27 at 17:05 +0530, Atul Gopinathan wrote: > > On Wed, Mar 31, 2021 at 08:28:15AM +0200, Greg KH wrote: > > > On Tue, Mar 30, 2021 at 10:36:52PM +0300, Pavel Skripkin wrote: > > > > Hi! > > > > > > > > I did some debugging on this > > > > https://syzkaller.appspot.com/bug?id=3ea507fb3c47426497b52bd82b8ef0dd5b6cc7ee > > > > and, I believe, I recognized the problem. The problem appears in > > > > case of > > > > ath9k_htc_hw_init() fail. In case of this fail all tx_buf->urb > > > > krefs will be > > > > initialized to 1, but in free function: > > > > > > > > static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb > > > > *hif_dev) > > > > > > > > .... > > > > > > > > static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb > > > > *hif_dev) > > > > { > > > > ... > > > > list_for_each_entry_safe(tx_buf, tx_buf_tmp, > > > > &hif_dev->tx.tx_buf, list) { > > > > usb_get_urb(tx_buf->urb); > > > > ... > > > > usb_free_urb(tx_buf->urb); > > > > ... > > > > } > > > > > > > > Krefs are incremented and then decremented, that means urbs > > > > won't be freed. > > > > I found your patch and I can't properly understand why You added > > > > usb_get_urb(tx_buf->urb). > > > > Can You explain please, I believe this will help me or somebody > > > > to fix this ussue :) > > > > > > I think almost everyone who has looked into this has given up due > > > to the > > > mess of twisty-passages here with almost no real-world benefits > > > for unwinding them :) > > > > Just wanted to confirm, what is the status of this bug then, as in > > is it > > invalid (not sure if that's the correct word)? I happened to stumble > > across the same syzkaller bug report Pavel posted above, in the > > morning. > > Saw that there has been no patch tests/fixes on this yet according > > to syzkaller. Spent a couple of hours going through it before > > sending a test patch to syzbot which returned an "OK" (and the > > patch is exactly what Pavel pointed out, I simply removed the > > `usb_get_urb()`). Before sending anything to the mailing list, I > > made sure to search all the relavant networking lists to see if > > this topic had been brought up (learnt > > to do this from my preious mistakes of sending already accepted > > patches) and > > luckily I found this. > > > > Syzbot has had 380 crashes caused by this bug, with the latest being > > today. So I wanted to confirm what should be done be about this > > bug. > > > > I saw on dashboard, that Dmitry tested latest upstream commit and > syzbot returned "OK", but usb_get_urb(tx_buf->urb); is still there. > I am sorry, I clicked wrong link on dashboard :( My bad. I believe, You can test your patch on this https://syzkaller.appspot.com/bug?id=cabffad18eb74197f84871802fd2c5117b61febf. usb_get_urb(tx_buf->urb) was introduced in patch related to this bug > I think, this usb_get_urb prevents race condition, but I'm not sure > about it, that's why I sent an email to patch author. As You can see, > he has not responded yet :) > > > Thank you! > > Atul > > With regards, > Pavel Skripkin > > With regards, Pavel Skripkin
