In the Linux kernel, the following vulnerability has been resolved:
bpf: Skip detached progs in trampoline images that are still in use
bpf_tramp_image_put() makes sure a trampoline image is not freed while
a task may still be running in it, but nothing similar is done for the
progs called by that image. Detach drops the last prog reference right
away and the prog is freed after grace periods, on the basis that a
task still in the traced function skips the fexit progs once the nop at
ip_after_call is patched to a jump.
That leaves out a task sleeping in a sleepable prog that runs before
the detached one, which no grace period waits for:
CPU 0 CPU 1
in image I, sleeping in prog S
detach P from I's trampoline
-> new image, bpf_tramp_image_put(I)
bpf_prog_put(P), last ref
grace periods, P freed
back from S
__bpf_prog_enter(P)
call P->bpf_func
If S and P are fexit progs the task is already past the patched jump,
and fentry only images don't have one. On x86 this is an int3 in
poisoned bpf_prog_pack memory:
Oops: int3: 0000 [#1] SMP NOPTI
CPU: 18 UID: 0 PID: 94573 Comm: x169 Not tainted 6.18.44 #1 PREEMPT(lazy)
RIP: 0010:0xffffffffc0601d8d
Call Trace:
Unknown