Executive brief
In the Linux kernel, the following vulnerability has been resolved:
bpf: Mark faultable stack helpers as sleepable
The faultable variants of bpf_get_stack() and bpf_get_task_stack() pass may_fault=true into the common stack collection code. Resolving user-space build IDs may then call build_id_parse_file() and block on filesystem reads.
Neither helper prototype sets might_sleep. Since prototype selection uses the sleepability of the whole program, the verifier can still allow these helpers from a non-sleepable region within that program, such as an explicit RCU or preemption-disabled region. The task-stack helper can also be called from a non-sleepable timer callback of a sleepable program.
Mark both faultable prototypes as sleepable. The existing helper context check then rejects these calls while continuing to allow them in genuinely sleepable contexts.