On Tue, Jan 28, 2020 at 02:14:57PM -0800, Guenter Roeck wrote: > With commit 216b44000ada ("brcmfmac: Fix use after free in > brcmf_sdio_readframes()") applied, we see locking timeouts in > brcmf_sdio_watchdog_thread(). > > brcmfmac: brcmf_escan_timeout: timer expired > INFO: task brcmf_wdog/mmc1:621 blocked for more than 120 seconds. > Not tainted 4.19.94-07984-g24ff99a0f713 #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > brcmf_wdog/mmc1 D 0 621 2 0x00000000 last_sleep: 2440793077. last_runnable: 2440766827 > [<c0aa1e60>] (__schedule) from [<c0aa2100>] (schedule+0x98/0xc4) > [<c0aa2100>] (schedule) from [<c0853830>] (__mmc_claim_host+0x154/0x274) > [<c0853830>] (__mmc_claim_host) from [<bf10c5b8>] (brcmf_sdio_watchdog_thread+0x1b0/0x1f8 [brcmfmac]) > [<bf10c5b8>] (brcmf_sdio_watchdog_thread [brcmfmac]) from [<c02570b8>] (kthread+0x178/0x180) > > In addition to restarting or exiting the loop, it is also necessary to > abort the command and to release the host. > > Fixes: 216b44000ada ("brcmfmac: Fix use after free in brcmf_sdio_readframes()") Huh... Thanks for fixing the bug. That seems to indicate that we were triggering the use after free but no one noticed at runtime. With kfree(), a use after free can be harmless if you don't have poisoning enabled and no other thread has re-used the memory. I'm not sure about kfree_skb() but presumably it's the same. Acked-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> regards, dan carpenter