From: Zou Wei zou_wei@huawei.com

mainline inclusion from mainline-v5.14-rc1 commit 34e7434ba4e97f4b85c1423a59b2922ba7dff2ea category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4DH CVE: CVE-2021-47355

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Zou Wei zou_wei@huawei.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/atm/nicstar.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/atm/nicstar.c b/drivers/atm/nicstar.c index cbec9adc01c7..2719f086abc7 100644 --- a/drivers/atm/nicstar.c +++ b/drivers/atm/nicstar.c @@ -296,7 +296,7 @@ static void __exit nicstar_cleanup(void) { XPRINTK("nicstar: nicstar_cleanup() called.\n");

- del_timer(&ns_timer); + del_timer_sync(&ns_timer);

pci_unregister_driver(&nicstar_driver);