From: Duoming Zhou <duoming@zju.edu.cn> mainline inclusion from mainline-v6.1-rc1 commit 175302f6b79ebbb207c2d58d6d3e679465de23b0 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4CC CVE: CVE-2021-47356 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The function hfcpci_softirq() is a timer handler. If it is running, the timer_pending() will return 0 and the del_timer_sync() in HFC_cleanup() will not be executed. As a result, the use-after-free bug will happen. The process is shown below: (cleanup routine) | (timer handler) HFC_cleanup() | hfcpci_softirq() if (timer_pending(&hfc_tl)) | del_timer_sync() | ... | ... pci_unregister_driver(hc) | driver_unregister | driver_for_each_device bus_remove_driver | _hfcpci_softirq driver_detach | ... put_device(dev) //[1]FREE | | dev_get_drvdata(dev) //[2]USE The device is deallocated is position [1] and used in position [2]. Fix by removing the "timer_pending" check in HFC_cleanup(), which makes sure that the hfcpci_softirq() have finished before the resource is deallocated. Fixes: 009fc857c5f6 ("mISDN: fix possible use-after-free in HFC_cleanup()") Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Xiang Yang <xiangyang3@huawei.com> --- drivers/isdn/hardware/mISDN/hfcpci.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c index 53349850f866..737a66a3dfde 100644 --- a/drivers/isdn/hardware/mISDN/hfcpci.c +++ b/drivers/isdn/hardware/mISDN/hfcpci.c @@ -2347,8 +2347,7 @@ HFC_init(void) static void __exit HFC_cleanup(void) { - if (timer_pending(&hfc_tl)) - del_timer_sync(&hfc_tl); + del_timer_sync(&hfc_tl); pci_unregister_driver(&hfc_driver); } -- 2.34.1