🛡️ AZL-69716 — kernel

CVE-2022-49764 affecting package kernel 5.15.200.1-1

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

bpf: Prevent bpf program recursion for raw tracepoint probes

We got report from sysbot [1] about warnings that were caused by

bpf program attached to contention_begin raw tracepoint triggering

the same tracepoint by using bpf_trace_printk helper that takes

trace_printk_lock lock.

Call Trace:

<TASK>

? trace_event_raw_event_bpf_trace_printk+0x5f/0x90

bpf_trace_printk+0x2b/0xe0

bpf_prog_a9aec6167c091eef_prog+0x1f/0x24

bpf_trace_run2+0x26/0x90

native_queued_spin_lock_slowpath+0x1c6/0x2b0

_raw_spin_lock_irqsave+0x44/0x50

bpf_trace_printk+0x3f/0xe0

bpf_prog_a9aec6167c091eef_prog+0x1f/0x24

bpf_trace_run2+0x26/0x90

native_queued_spin_lock_slowpath+0x1c6/0x2b0

_raw_spin_lock_irqsave+0x44/0x50

bpf_trace_printk+0x3f/0xe0

bpf_prog_a9aec6167c091eef_prog+0x1f/0x24

bpf_trace_run2+0x26/0x90

native_queued_spin_lock_slowpath+0x1c6/0x2b0

_raw_spin_lock_irqsave+0x44/0x50

bpf_trace_printk+0x3f/0xe0

bpf_prog_a9aec6167c091eef_prog+0x1f/0x24

bpf_trace_run2+0x26/0x90

native_queued_spin_lock_slowpath+0x1c6/0x2b0

_raw_spin_lock_irqsave+0x44/0x50

__unfreeze_partials+0x5b/0x160

...

The can be reproduced by attaching bpf program as raw tracepoint on

contention_begin tracepoint. The bpf prog calls bpf_trace_printk

helper. Then by running perf bench the spin lock code is forced to

take slow path and call contention_begin tracepoint.

Fixing this by skipping execution of the bpf program if it's

already running, Using bpf prog 'active' field, which is being

currently used by trampoline programs for the same reason.

Moving bpf_prog_inc_misses_counter to syscall.c because

trampoline.c is compiled in just for CONFIG_BPF_JIT option.

[1] https://lore.kernel.org/bpf/YxhFe3EwqchC%2FfYf@krava/T/#t