From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- tools/verification/models/rtapp/pagefault.ltl | 1 + tools/verification/models/rtapp/sleep.ltl | 20 ++++++++++++++++++++ tools/verification/models/rtapp/wakeup.ltl | 5 +++++ 3 files changed, 26 insertions(+) create mode 100644 tools/verification/models/rtapp/pagefault.ltl create mode 100644 tools/verification/models/rtapp/sleep.ltl create mode 100644 tools/verification/models/rtapp/wakeup.ltl (limited to 'tools/verification/models/rtapp') diff --git a/tools/verification/models/rtapp/pagefault.ltl b/tools/verification/models/rtapp/pagefault.ltl new file mode 100644 index 000000000..d7ce62102 --- /dev/null +++ b/tools/verification/models/rtapp/pagefault.ltl @@ -0,0 +1 @@ +RULE = always (RT imply not PAGEFAULT) diff --git a/tools/verification/models/rtapp/sleep.ltl b/tools/verification/models/rtapp/sleep.ltl new file mode 100644 index 000000000..4d78fdd20 --- /dev/null +++ b/tools/verification/models/rtapp/sleep.ltl @@ -0,0 +1,20 @@ +RULE = always ((RT and SLEEP and USER_THREAD) imply (RT_FRIENDLY_SLEEP or ALLOWLIST)) + +RT_FRIENDLY_SLEEP = RT_VALID_SLEEP_REASON + and ((not SCHEDULE_IN) until RT_FRIENDLY_WAKE) + +RT_VALID_SLEEP_REASON = FUTEX_WAIT + or RT_FRIENDLY_NANOSLEEP + or EPOLL_WAIT + +RT_FRIENDLY_NANOSLEEP = CLOCK_NANOSLEEP + and NANOSLEEP_TIMER_ABSTIME + and not NANOSLEEP_CLOCK_REALTIME + +RT_FRIENDLY_WAKE = WOKEN_BY_EQUAL_OR_HIGHER_PRIO + or WOKEN_BY_HARDIRQ + or WOKEN_BY_NMI + or ABORT_SLEEP + +ALLOWLIST = BLOCK_ON_RT_MUTEX + or FUTEX_LOCK_PI diff --git a/tools/verification/models/rtapp/wakeup.ltl b/tools/verification/models/rtapp/wakeup.ltl new file mode 100644 index 000000000..a5d63ca08 --- /dev/null +++ b/tools/verification/models/rtapp/wakeup.ltl @@ -0,0 +1,5 @@ +RULE = always (((RT and USER_THREAD) imply + (not (WOKEN_BY_LOWER_PRIO or WOKEN_BY_SOFTIRQ)) or ALLOWLIST)) + +ALLOWLIST = BLOCK_ON_RT_MUTEX + or FUTEX_LOCK_PI -- cgit v1.3.1