CVE-2023-1118: Use After Free

A flaw in the Linux Kernel found. There are use-after-free vulnerabilities in drivers/media/rc/eneir.c of linux that allow attacker to crash linux kernel without any privilege by detaching rc device.

When the rc device is detaching, function eneremove() will be called. But the synchronizations in eneremove() are bad. The situations that may lead to race conditions are shown below.

Firstly, the rx receiver is disabled with enerxdisable() before rcunregisterdevice() in eneremove(), which means it can be enabled again if a process opens /dev/lirc0 between enerxdisable() and rcunregisterdevice().

(cleanup routine) | (open routine) eneremove() | enerxdisable(dev); | eneopen() | enerxenable(dev); //re-enable!

Secondly, the irqaction descriptor is freed by freeirq() before the rc device is unregistered, which means irqaction descriptor may be accessed again after it is deallocated.

(free routine) | (use routine) eneremove() | enerxenable() freeirq(dev->irq, ...); //FREE | enerxenablehw() | enewritereg(..., dev->irq << 1) //USE |

Thirdly, the timer can call enetxsample() that can write to the io ports, which means the io ports could be accessed again after they are deallocated by releaseregion().

(free routine) | (use routine) eneremove() | enetxsample() releaseregion(dev->hwio, ...); //FREE | enewritereg() | outb(..., dev->hwio + ENEIO) //USE

Fourthly, there is no function to cancel txsimtimer in eneremove(), the timer handler enetxirqsim() could race with eneremove(). As a result, the UAF bugs could happen, the process is shown below.

(free routine) | (use routine) | modtimer(&dev->txsimtimer, ..) eneremove() | (wait a time) kfree(dev) //FREE | enetxirqsim() | dev->hwlock //USE | enetxsample(dev) //USE

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Reference: https://github.com/torvalds/linux/commit/29b0589a865b6f66d141d79b2dd1373e4e50fe17