On Thu, Oct 27, 2022 at 3:03 AM 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--;".
>
> In addition, function __check_func_call() has a similar problem. In
> the abnormal scenario before "state->curframe++;", the callee is alse
> not released.
For prepare_func_exit, wouldn't it be correct and cleaner to just move
state->curframe--; to the very bottom of the function, right when we
free callee and reset frame[] pointer to NULL?
For __check_func_call, please use err_out label name to disambiguate
it from the "err" variable.
>
> 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 | 25 ++++++++++++++++---------
> 1 file changed, 16 insertions(+), 9 deletions(-)
>
[...]
