CVE-2024-35895

In the Linux kernel, the following vulnerability has been resolved: bpf,
sockmap: Prevent lock inversion deadlock in map delete elem syzkaller
started using corpuses where a BPF tracing program deletes elements from a
sockmap/sockhash map. Because BPF tracing programs can be invoked from any
interrupt context, locks taken during a map_delete_elem operation must be
hardirq-safe. Otherwise a deadlock due to lock inversion is possible, as
reported by lockdep: CPU0 CPU1 ---- ---- lock(&htab->buckets[i].lock);
local_irq_disable(); lock(&host->lock); lock(&htab->buckets[i].lock);
<Interrupt> lock(&host->lock); Locks in sockmap are hardirq-unsafe by
design. We expects elements to be deleted from sockmap/sockhash only in
task (normal) context with interrupts enabled, or in softirq context.
Detect when map_delete_elem operation is invoked from a context which is
not hardirq-unsafe, that is interrupts are disabled, and bail out with an
error. Note that map updates are not affected by this issue. BPF verifier
does not allow updating sockmap/sockhash from a BPF tracing program today.