From: Thomas Gleixner <tglx@linutronix.de>
To: David Miller <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
netdev@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
bigeasy@linutronix.de, peterz@infradead.org, williams@redhat.com,
rostedt@goodmis.org, juri.lelli@redhat.com, mingo@kernel.org
Subject: [PATCH] bpf: Enforce map preallocation for all instrumentation programs
Date: Mon, 17 Feb 2020 13:59:12 +0100 [thread overview]
Message-ID: <875zg5pdy7.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87pneht3re.fsf@nanos.tec.linutronix.de>
The assumption that only programs attached to perf NMI events can deadlock
on memory allocators is wrong. Assume the following simplified callchain:
kmalloc() from regular non BPF context
cache empty
freelist empty
lock(zone->lock);
tracepoint or kprobe
BPF()
update_elem()
lock(bucket)
kmalloc()
cache empty
freelist empty
lock(zone->lock); <- DEADLOCK
There are also other ways to create wreckage:
kmalloc() from regular non BPF context
local_irq_save();
...
obj = slab_first();
kprobe()
BPF()
update_elem()
lock(bucket)
kmalloc()
local_irq_save();
...
obj = slab_first(); <- Same object as above ...
So preallocation _must_ be enforced for all variants of intrusive
instrumentation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/bpf/verifier.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8144,19 +8144,23 @@ static int check_map_prog_compatibility(
struct bpf_prog *prog)
{
- /* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use
- * preallocated hash maps, since doing memory allocation
- * in overflow_handler can crash depending on where nmi got
- * triggered.
+ /*
+ * Make sure that trace type programs use preallocated hash maps.
+ * Perf programs obviously can't do memory allocation in NMI
+ * context and all other types can deadlock on a memory allocator
+ * lock when a tracepoint/kprobe triggers a BPF program inside a
+ * lock held region or create inconsistent state when the probe is
+ * within an interrupts disabled critical region in the memory
+ * allocator.
*/
- if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
+ if ((is_tracing_prog_type(prog->type)) {
if (!check_map_prealloc(map)) {
- verbose(env, "perf_event programs can only use preallocated hash map\n");
+ verbose(env, "tracing programs can only use preallocated hash map\n");
return -EINVAL;
}
if (map->inner_map_meta &&
!check_map_prealloc(map->inner_map_meta)) {
- verbose(env, "perf_event programs can only use preallocated inner hash map\n");
+ verbose(env, "tracing programs can only use preallocated inner hash map\n");
return -EINVAL;
}
}
next prev parent reply other threads:[~2020-02-17 12:59 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 13:39 [RFC patch 00/19] bpf: Make BPF and PREEMPT_RT co-exist Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 01/19] sched: Provide migrate_disable/enable() inlines Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 02/19] sched: Provide cant_migrate() Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 03/19] bpf: Update locking comment in hashtab code Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 04/19] bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run() Thomas Gleixner
2020-02-19 16:54 ` Steven Rostedt
2020-02-19 17:26 ` Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 05/19] perf/bpf: Remove preempt disable around BPF invocation Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 06/19] bpf: Dont iterate over possible CPUs with interrupts disabled Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 07/19] bpf: Provide BPF_PROG_RUN_PIN_ON_CPU() macro Thomas Gleixner
2020-02-14 18:50 ` Mathieu Desnoyers
2020-02-14 19:36 ` Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 08/19] bpf: Replace cant_sleep() with cant_migrate() Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 09/19] bpf: Use BPF_PROG_RUN_PIN_ON_CPU() at simple call sites Thomas Gleixner
2020-02-19 1:39 ` Vinicius Costa Gomes
2020-02-19 9:00 ` Thomas Gleixner
2020-02-19 16:38 ` Alexei Starovoitov
2020-02-21 0:20 ` Kees Cook
2020-02-21 14:00 ` Thomas Gleixner
2020-02-21 14:05 ` Peter Zijlstra
2020-02-21 22:15 ` Kees Cook
2020-02-14 13:39 ` [RFC patch 10/19] trace/bpf: Use migrate disable in trace_call_bpf() Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 11/19] bpf/tests: Use migrate disable instead of preempt disable Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 12/19] bpf: Use migrate_disable/enabe() in trampoline code Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 13/19] bpf: Use migrate_disable/enable in array macros and cgroup/lirc code Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 14/19] bpf: Use migrate_disable() in hashtab code Thomas Gleixner
2020-02-14 19:11 ` Mathieu Desnoyers
2020-02-14 19:56 ` Thomas Gleixner
2020-02-18 23:36 ` Alexei Starovoitov
2020-02-19 0:49 ` Thomas Gleixner
2020-02-19 1:23 ` Alexei Starovoitov
2020-02-19 15:17 ` Mathieu Desnoyers
2020-02-20 4:19 ` Alexei Starovoitov
2020-02-14 13:39 ` [RFC patch 15/19] bpf: Use migrate_disable() in sys_bpf() Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 16/19] bpf: Factor out hashtab bucket lock operations Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 17/19] bpf: Prepare hashtab locking for PREEMPT_RT Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 18/19] bpf, lpm: Make locking RT friendly Thomas Gleixner
2020-02-14 13:39 ` [RFC patch 19/19] bpf/stackmap: Dont trylock mmap_sem with PREEMPT_RT and interrupts disabled Thomas Gleixner
2020-02-14 17:53 ` [RFC patch 00/19] bpf: Make BPF and PREEMPT_RT co-exist David Miller
2020-02-14 18:36 ` Thomas Gleixner
2020-02-17 12:59 ` Thomas Gleixner [this message]
2020-02-15 20:09 ` Jakub Kicinski
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