Re: [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file

Drew Fustini
2021-02-10T19:06:06Z

On Wed, Feb 10, 2021 at 09:20:44PM +0300, Dan Carpenter wrote:
> Hi Drew,
>
> url: https://github.com/0day-ci/linux/commits/Drew-Fustini/pinctrl-pinmux-Add-pinmux-select-debugfs-file/20210210-160108
> base: https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git devel
> config: i386-randconfig-m021-20210209 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

Does it makes sense for me to include that tag in this patch?

It's not really a fix but rather creating a new feature through debugfs.
I am wondering if it might confuse people reading the git log as to
whether the Reported-by: was with regards to the addition of
'pinmux-select' to debugfs, rather than it was just reporting that my
goto handling was incorrect.

I think it makes sense for me to mention that in the PATCH changelog but
that won't be in the git commit message.

>
> smatch warnings:
> drivers/pinctrl/pinmux.c:762 pinmux_select() error: uninitialized symbol 'gname'.
>
> vim +/gname +762 drivers/pinctrl/pinmux.c
>
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 678 static ssize_t pinmux_select(struct file *file, const char __user *user_buf,
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 679 size_t len, loff_t *ppos)
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 680 {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 681 struct seq_file *sfile = file->private_data;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 682 struct pinctrl_dev *pctldev = sfile->private;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 683 const struct pinmux_ops *pmxops = pctldev->desc->pmxops;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 684 const char *const *groups;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 685 char *buf, *fname, *gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 686 unsigned int num_groups;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 687 int fsel, gsel, ret;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 688
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 689 if (len > (PINMUX_MAX_NAME * 2)) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 690 dev_err(pctldev->dev, "write too big for buffer");
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 691 return -EINVAL;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 692 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 693
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 694 buf = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME * 2, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 695 if (!buf)
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 696 return -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 697
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 698 fname = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 699 if (!fname) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 700 ret = -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 701 goto free_buf;
>
> The gotos are out of order. They should be in mirror/reverse order of
> the allocations:
>
> free_gmane:
> devm_kfree(pctldev->dev, gname);
> free_fname:
> devm_kfree(pctldev->dev, fname);
> free_buf:
> devm_kfree(pctldev->dev, buf);

Thank you, yes, I should have caught this.

>
> But also why do we need to use devm_kfree() at all? I thought the whole
> point of devm_ functions was that they are garbage collected
> automatically for you. Can we not just delete all error handling and
> return -ENOMEM here?

Andy replied already that it is incorrect for me to be using devm_*() in
the debugfs write operation. I'll be changing the code to use normal
kzalloc() and thus will need to keep the goto error handling (but with
the correct order as you pointed out).

>
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 702 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 703
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 704 gname = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 705 if (!buf) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 706 ret = -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 707 goto free_fname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 708 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 709
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 710 ret = strncpy_from_user(buf, user_buf, PINMUX_MAX_NAME * 2);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 711 if (ret < 0) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 712 dev_err(pctldev->dev, "failed to copy buffer from userspace");
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 713 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 714 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 715 buf[len-1] = '\0';
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 716
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 717 ret = sscanf(buf, "%s %s", fname, gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 718 if (ret != 2) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 719 dev_err(pctldev->dev, "expected format: <function-name> <group-name>");
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 720 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 721 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 722
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 723 fsel = pinmux_func_name_to_selector(pctldev, fname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 724 if (fsel < 0) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 725 dev_err(pctldev->dev, "invalid function %s in map table\n", fname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 726 ret = -EINVAL;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 727 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 728 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 729
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 730 ret = pmxops->get_function_groups(pctldev, fsel, &groups, &num_groups);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 731 if (ret) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 732 dev_err(pctldev->dev, "no groups for function %d (%s)", fsel, fname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 733 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 734
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 735 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 736
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 737 ret = match_string(groups, num_groups, gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 738 if (ret < 0) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 739 dev_err(pctldev->dev, "invalid group %s", gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 740 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 741 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 742
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 743 ret = pinctrl_get_group_selector(pctldev, gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 744 if (ret < 0) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 745 dev_err(pctldev->dev, "failed to get group selectorL %s", gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 746 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 747 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 748 gsel = ret;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 749
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 750 ret = pmxops->set_mux(pctldev, fsel, gsel);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 751 if (ret) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 752 dev_err(pctldev->dev, "set_mux() failed: %d", ret);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 753 goto free_gname;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 754 }
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 755
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 756 return len;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 757 free_buf:
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 758 devm_kfree(pctldev->dev, buf);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 759 free_fname:
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 760 devm_kfree(pctldev->dev, fname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 761 free_gname:
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 @762 devm_kfree(pctldev->dev, gname);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 763 return ret;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 764 }
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Thank you,
Drew