Re: [PATCH 1/2] tracing: Fix kmemleak in tracing_map_array_free

[Chunyu Hu]

Resend to add linux-kernel cced. The steps I was using was:

echo hist:keys=irq > trigger
echo '!hist:keys=irq:vals=hitcount:sort=hitcount:size=2048' >  trigger

Then scan the kmem.
echo scan > /sys/kernel/debug/kmemleak

On 14 August 2017 at 18:18, Chunyu Hu <chuhu@xxxxxxxxxx> wrote:
> kmemleak reported the below leak when I was doing clear of the hist
> trigger. With this patch, the kmeamleak is gone.
>
> unreferenced object 0xffff94322b63d760 (size 32):
>   comm "bash", pid 1522, jiffies 4403687962 (age 2442.311s)
>   hex dump (first 32 bytes):
>     00 01 00 00 04 00 00 00 08 00 00 00 ff 00 00 00  ................
>     10 00 00 00 00 00 00 00 80 a8 7a f2 31 94 ff ff  ..........z.1...
>   backtrace:
>     [<ffffffff9e96c27a>] kmemleak_alloc+0x4a/0xa0
>     [<ffffffff9e424cba>] kmem_cache_alloc_trace+0xca/0x1d0
>     [<ffffffff9e377736>] tracing_map_array_alloc+0x26/0x140
>     [<ffffffff9e261be0>] kretprobe_trampoline+0x0/0x50
>     [<ffffffff9e38b935>] create_hist_data+0x535/0x750
>     [<ffffffff9e38bd47>] event_hist_trigger_func+0x1f7/0x420
>     [<ffffffff9e38893d>] event_trigger_write+0xfd/0x1a0
>     [<ffffffff9e44dfc7>] __vfs_write+0x37/0x170
>     [<ffffffff9e44f552>] vfs_write+0xb2/0x1b0
>     [<ffffffff9e450b85>] SyS_write+0x55/0xc0
>     [<ffffffff9e203857>] do_syscall_64+0x67/0x150
>     [<ffffffff9e977ce7>] return_from_SYSCALL_64+0x0/0x6a
>     [<ffffffffffffffff>] 0xffffffffffffffff
> unreferenced object 0xffff9431f27aa880 (size 128):
>   comm "bash", pid 1522, jiffies 4403687962 (age 2442.311s)
>   hex dump (first 32 bytes):
>     00 00 8c 2a 32 94 ff ff 00 f0 8b 2a 32 94 ff ff  ...*2......*2...
>     00 e0 8b 2a 32 94 ff ff 00 d0 8b 2a 32 94 ff ff  ...*2......*2...
>   backtrace:
>     [<ffffffff9e96c27a>] kmemleak_alloc+0x4a/0xa0
>     [<ffffffff9e425348>] __kmalloc+0xe8/0x220
>     [<ffffffff9e3777c1>] tracing_map_array_alloc+0xb1/0x140
>     [<ffffffff9e261be0>] kretprobe_trampoline+0x0/0x50
>     [<ffffffff9e38b935>] create_hist_data+0x535/0x750
>     [<ffffffff9e38bd47>] event_hist_trigger_func+0x1f7/0x420
>     [<ffffffff9e38893d>] event_trigger_write+0xfd/0x1a0
>     [<ffffffff9e44dfc7>] __vfs_write+0x37/0x170
>     [<ffffffff9e44f552>] vfs_write+0xb2/0x1b0
>     [<ffffffff9e450b85>] SyS_write+0x55/0xc0
>     [<ffffffff9e203857>] do_syscall_64+0x67/0x150
>     [<ffffffff9e977ce7>] return_from_SYSCALL_64+0x0/0x6a
>     [<ffffffffffffffff>] 0xffffffffffffffff
>
> Signed-off-by: Chunyu Hu <chuhu@xxxxxxxxxx>
> ---
>  kernel/trace/tracing_map.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
> index 0a689bb..305039b 100644
> --- a/kernel/trace/tracing_map.c
> +++ b/kernel/trace/tracing_map.c
> @@ -221,16 +221,19 @@ void tracing_map_array_free(struct tracing_map_array *a)
>         if (!a)
>                 return;
>
> -       if (!a->pages) {
> -               kfree(a);
> -               return;
> -       }
> +       if (!a->pages)
> +               goto free;
>
>         for (i = 0; i < a->n_pages; i++) {
>                 if (!a->pages[i])
>                         break;
>                 free_page((unsigned long)a->pages[i]);
>         }
> +
> +       kfree(a->pages);
> +
> + free:
> +       kfree(a);
>  }
>
>  struct tracing_map_array *tracing_map_array_alloc(unsigned int n_elts,
> --
> 1.8.3.1
>