On Thu, Oct 27, 2022 at 10:01 PM Wang Yufen <wangyufen@xxxxxxxxxx> wrote:
>
> kmemleak reports this issue:
>
> unreferenced object 0xffff88817139d000 (size 2048):
> comm "test_progs", pid 33246, jiffies 4307381979 (age 45851.820s)
> hex dump (first 32 bytes):
> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<0000000045f075f0>] kmalloc_trace+0x27/0xa0
> [<0000000098b7c90a>] __check_func_call+0x316/0x1230
> [<00000000b4c3c403>] check_helper_call+0x172e/0x4700
> [<00000000aa3875b7>] do_check+0x21d8/0x45e0
> [<000000001147357b>] do_check_common+0x767/0xaf0
> [<00000000b5a595b4>] bpf_check+0x43e3/0x5bc0
> [<0000000011e391b1>] bpf_prog_load+0xf26/0x1940
> [<0000000007f765c0>] __sys_bpf+0xd2c/0x3650
> [<00000000839815d6>] __x64_sys_bpf+0x75/0xc0
> [<00000000946ee250>] do_syscall_64+0x3b/0x90
> [<0000000000506b7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> The root case here is: In function prepare_func_exit(), the callee is
> not released in the abnormal scenario after "state->curframe--;". To
> fix, move "state->curframe--;" to the very bottom of the function,
> right when we free callee and reset frame[] pointer to NULL, as Andrii
> suggested.
>
> In addition, function __check_func_call() has a similar problem. In
> the abnormal scenario before "state->curframe++;", the callee is alse
> not released.
>
> Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
> Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier")
> Signed-off-by: Wang Yufen <wangyufen@xxxxxxxxxx>
> ---
This change seems to be breaking BPF selftests quite badly, please
check what's going on ([0]):
[0] https://github.com/kernel-patches/bpf/actions/runs/3379444311/jobs/5611599540
> kernel/bpf/verifier.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 014ee09..d28d460 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -6736,11 +6736,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn
> /* Transfer references to the callee */
> err = copy_reference_state(callee, caller);
> if (err)
> - return err;
> + goto err_out;
>
> err = set_callee_state_cb(env, caller, callee, *insn_idx);
> if (err)
> - return err;
> + goto err_out;
>
> clear_caller_saved_regs(env, caller->regs);
>
> @@ -6757,6 +6757,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn
> print_verifier_state(env, callee, true);
> }
> return 0;
> +
> +err_out:
> + kfree(callee);
> + state->frame[state->curframe + 1] = NULL;
> + return err;
> }
>
> int map_set_for_each_callback_args(struct bpf_verifier_env *env,
> @@ -6969,7 +6974,6 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
> return -EINVAL;
> }
>
> - state->curframe--;
> caller = state->frame[state->curframe];
> if (callee->in_callback_fn) {
> /* enforce R0 return value range [0, 1]. */
> @@ -7000,6 +7004,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
> return err;
> }
>
> + state->curframe--;
> *insn_idx = callee->callsite + 1;
> if (env->log.level & BPF_LOG_LEVEL) {
> verbose(env, "returning from callee:\n");
> --
> 1.8.3.1
>
