ipv6/addrconf: fix a potential refcount underflow for idev

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ipv6/addrconf: fix a potential refcount underflow for idev Now in addrconf_mod_rs_timer(), reference idev depends on whether rs_timer is not pending. Then modify rs_timer timeout. There is a time gap in [1], during which if the pending rs_timer becomes not pending. It will miss to hold idev, but the rs_timer is activated. Thus rs_timer callback function addrconf_rs_timer() will be executed and put idev later without holding idev. A refcount underflow issue for idev can be caused by this. if (!timer_pending(&idev->rs_timer)) in6_dev_hold(idev); <--------------[1] mod_timer(&idev->rs_timer, jiffies + when); To fix the issue, hold idev if mod_timer() return 0.

References

• https://git.kernel.org/stable/c/c6395e32935d35e6f935e7caf1c2dac5a95943b4
• https://git.kernel.org/stable/c/df62fdcd004afa72ecbed0e862ebb983acd3aa57
• https://git.kernel.org/stable/c/c7eeba47058532f6077d6a658e38b6698f6ae71a
• https://git.kernel.org/stable/c/2ad31ce40e8182860b631e37209e93e543790b7c
• https://git.kernel.org/stable/c/82abd1c37d3bf2a2658b34772c17a25a6f9cca42
• https://git.kernel.org/stable/c/436b7cc7eae7851c184b671ed7a4a64c750b86f7
• https://git.kernel.org/stable/c/1f656e483eb4733d62f18dfb206a49b78f60f495
• https://git.kernel.org/stable/c/06a0716949c22e2aefb648526580671197151acc