CVE-2026-74477

In the Linux kernel, the following vulnerability has been resolved:

uprobes: Fix NULL pointer dereference in hprobe_expire()

Forking a task that has a pending uretprobe can oops the kernel with a NULL pointer dereference in the clone() path:

BUG: kernel NULL pointer dereference, address: 0000000000000018 Oops: 0002 [#1] SMP NOPTI RIP: 0010:hprobeexpire CR2: 0000000000000018 Call Trace: uprobecopyprocess copyprocess kernel_clone __x64sysclone dosyscall64 entrySYSCALL64afterhwframe

This was found on real hosts on Meta fleet.

I've got the impression that this is what is happening:

CPU 1 CPU 2 (traced task) ----- ------------------- hit uprobe, prepareuretprobe(): hprobe LEASED, refcount >= 1 uprobeunregister() putuprobe(): refcount -> 0 fork() -> duputask() hprobeexpire(hprobe, true) trygetuprobe() -> NULL getuprobe(NULL) <-- Oops

Only take the extra reference when the uprobe is non-NULL; a NULL means it is gone and is the correct value to return.