在 2022/11/3 3:05, Andrii Nakryiko 写道:
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/5611599540kernel/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];
Got the wrong “caller” here, will change to state->frame[state->curframe - 1] in v3
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
