driver core: fix potential NULL pointer dereference in dev_uevent()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: driver core: fix potential NULL pointer dereference in dev_uevent() If userspace reads "uevent" device attribute at the same time as another threads unbinds the device from its driver, change to dev->driver from a valid pointer to NULL may result in crash. Fix this by using READ_ONCE() when fetching the pointer, and take bus' drivers klist lock to make sure driver instance will not disappear while we access it. Use WRITE_ONCE() when setting the driver pointer to ensure there is no tearing.

References

• https://git.kernel.org/stable/c/abe56be73eb10a677d16066f65ff9d30251f5eee
• https://git.kernel.org/stable/c/2b344e779d9afd0fcb5ee4000e4d0fc7d8d867eb
• https://git.kernel.org/stable/c/3781e4b83e174364998855de777e184cf0b62c40
• https://git.kernel.org/stable/c/18daa52418e7e4629ed1703b64777294209d2622