From: Artem Savkov <asavkov@redhat.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, netdev@vger.kernel.org, jolsa@kernel.org
Cc: linux-kernel@vger.kernel.org, Artem Savkov <asavkov@redhat.com>,
Yonghong Song <yonghong.song@linux.dev>
Subject: [PATCH bpf-next v2] selftests/bpf: fix potential premature unload in bpf_testmod
Date: Wed, 10 Jan 2024 09:57:37 +0100 [thread overview]
Message-ID: <20240110085737.8895-1-asavkov@redhat.com> (raw)
In-Reply-To: <82f55c0e-0ec8-4fe1-8d8c-b1de07558ad9@linux.dev>
It is possible for bpf_kfunc_call_test_release() to be called from
bpf_map_free_deferred() when bpf_testmod is already unloaded and
perf_test_stuct.cnt which it tries to decrease is no longer in memory.
This patch tries to fix the issue by waiting for all references to be
dropped in bpf_testmod_exit().
The issue can be triggered by running 'test_progs -t map_kptr' in 6.5,
but is obscured in 6.6 by d119357d07435 ("rcu-tasks: Treat only
synchronous grace periods urgently").
Fixes: 65eb006d85a2a ("bpf: Move kernel test kfuncs to bpf_testmod")
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 91907b321f913..e7c9e1c7fde04 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -2,6 +2,7 @@
/* Copyright (c) 2020 Facebook */
#include <linux/btf.h>
#include <linux/btf_ids.h>
+#include <linux/delay.h>
#include <linux/error-injection.h>
#include <linux/init.h>
#include <linux/module.h>
@@ -544,6 +545,14 @@ static int bpf_testmod_init(void)
static void bpf_testmod_exit(void)
{
+ /* Need to wait for all references to be dropped because
+ * bpf_kfunc_call_test_release() which currently resides in kernel can
+ * be called after bpf_testmod is unloaded. Once release function is
+ * moved into the module this wait can be removed.
+ */
+ while (refcount_read(&prog_test_struct.cnt) > 1)
+ msleep(20);
+
return sysfs_remove_bin_file(kernel_kobj, &bin_attr_bpf_testmod_file);
}
--
2.43.0
next prev parent reply other threads:[~2024-01-10 8:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-09 16:43 [PATCH bpf-next] selftests/bpf: fix potential premature unload in bpf_testmod Artem Savkov
2024-01-09 19:40 ` Yonghong Song
2024-01-10 8:14 ` Artem Savkov
2024-01-10 12:49 ` Jiri Olsa
2024-01-10 8:57 ` Artem Savkov [this message]
2024-01-16 15:50 ` [PATCH bpf-next v2] " patchwork-bot+netdevbpf
2024-01-16 16:58 ` Jiri Olsa
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