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authorThomas Gleixner <tglx@linutronix.de>2020-02-24 17:01:33 +0300
committerAlexei Starovoitov <ast@kernel.org>2020-02-25 03:12:19 +0300
commit2ed905c521e56aead6987df94c083efb0ee59895 (patch)
treeda9db871359f60fed6910b5df34298e5ecada9a6 /kernel
parent94dacdbd5d2dfa2cffd308f128d78c99f855f5be (diff)
downloadlinux-2ed905c521e56aead6987df94c083efb0ee59895.tar.xz
bpf: Enforce preallocation for instrumentation programs on RT
Aside of the general unsafety of run-time map allocation for instrumentation type programs RT enabled kernels have another constraint: The instrumentation programs are invoked with preemption disabled, but the memory allocator spinlocks cannot be acquired in atomic context because they are converted to 'sleeping' spinlocks on RT. Therefore enforce map preallocation for these programs types when RT is enabled. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200224145642.648784007@linutronix.de
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 532b7b0320ba..289383edfc8c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8168,16 +8168,21 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
* of the memory allocator or at a place where a recursion into the
* memory allocator would see inconsistent state.
*
- * For now running such programs is allowed for backwards
- * compatibility reasons, but warnings are emitted so developers are
- * made aware of the unsafety and can fix their programs before this
- * is enforced.
+ * On RT enabled kernels run-time allocation of all trace type
+ * programs is strictly prohibited due to lock type constraints. On
+ * !RT kernels it is allowed for backwards compatibility reasons for
+ * now, but warnings are emitted so developers are made aware of
+ * the unsafety and can fix their programs before this is enforced.
*/
if (is_tracing_prog_type(prog->type) && !is_preallocated_map(map)) {
if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
verbose(env, "perf_event programs can only use preallocated hash map\n");
return -EINVAL;
}
+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ verbose(env, "trace type programs can only use preallocated hash map\n");
+ return -EINVAL;
+ }
WARN_ONCE(1, "trace type BPF program uses run-time allocation\n");
verbose(env, "trace type programs with run-time allocated hash maps are unsafe. Switch to preallocated hash maps.\n");
}