From: Artem Savkov asavkov@redhat.com
[ Upstream commit d177c1be06ce28aa8c8710ac55be1b5ad3f314c6 ]
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: 65eb006d85a2 ("bpf: Move kernel test kfuncs to bpf_testmod") Signed-off-by: Artem Savkov asavkov@redhat.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Yonghong Song yonghong.song@linux.dev Cc: Jiri Olsa jolsa@kernel.org Link: https://lore.kernel.org/bpf/82f55c0e-0ec8-4fe1-8d8c-b1de07558ad9@linux.dev Link: https://lore.kernel.org/bpf/20240110085737.8895-1-asavkov@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 cefc5dd72573c..2e8adf059fa3b 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> @@ -541,6 +542,14 @@ 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); }