在 2022/11/8 8:46, Martin KaFai Lau 写道:
On 11/3/22 2:42 AM, Wang Yufen 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>
---
kernel/bpf/verifier.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7f0a9f6..eff7a5a 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);
Is it sure that free_func_state() is not needed ?
No, free_func_state() is needed. Sorry, I didn't notice that memory is
alloced for callee->refs in
copy_reference_state()-> copy_array() -> kmalloc_track_caller(). will
change in v4
Thanks.
Wang
+ state->frame[state->curframe + 1] = NULL;
+ return err;
}
int map_set_for_each_callback_args(struct bpf_verifier_env *env,
@@ -6970,8 +6975,7 @@ static int prepare_func_exit(struct
bpf_verifier_env *env, int *insn_idx)
return -EINVAL;
}
- state->curframe--;
- caller = state->frame[state->curframe];
+ caller = state->frame[state->curframe - 1];
if (callee->in_callback_fn) {
/* enforce R0 return value range [0, 1]. */
struct tnum range = callee->callback_ret_range;
@@ -7001,6 +7005,7 @@ static int prepare_func_exit(struct
bpf_verifier_env *env, int *insn_idx)
return err;
}
+ state->curframe--;
nit. state->curframe is always pointing to callee upto this point?
Instead of doing another +1 dance in the latter
'state->frame[state->curframe + 1] = NULL;', how about do it later like:
/* clear everything in the callee */
free_func_state(callee);
state->frame[state->curframe--] = NULL;
It shouldn't affect the earlier print_verifier_state() which
explicitly takes callee and caller as its arg, right?
Yes, state->curframe not affect print_verifier_state(), doing
"state->curframe--" at the end of the function is better, also will
change in v4. Thanks!
*insn_idx = callee->callsite + 1;
if (env->log.level & BPF_LOG_LEVEL) {
verbose(env, "returning from callee:\n");
