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SubjectRe: [PATCH net v2 2/3] net: core: add netdev_class_has_file_ns() helper function
On Sat, Apr 04, 2020 at 02:19:09PM +0000, Taehee Yoo wrote:
> This helper function is to check whether the class file "/sys/class/net/*"
> is existing or not.
> In the next patch, this helper function will be used.
>
> Reported-by: syzbot+830c6dbfc71edc4f0b8f@syzkaller.appspotmail.com
> Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
> Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> ---
>
> v1 -> v2:
> - use class_has_file_ns(), which is introduced by the first patch.
>
> include/linux/netdevice.h | 2 +-
> net/core/net-sysfs.c | 6 ++++++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 130a668049ab..a04c487c0975 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -4555,7 +4555,7 @@ int netdev_class_create_file_ns(const struct class_attribute *class_attr,
> const void *ns);
> void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
> const void *ns);
> -
> +bool netdev_class_has_file_ns(const char *name, const void *ns);
> static inline int netdev_class_create_file(const struct class_attribute *class_attr)
> {
> return netdev_class_create_file_ns(class_attr, NULL);
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index cf0215734ceb..8a20d658eff0 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -1914,6 +1914,12 @@ void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
> }
> EXPORT_SYMBOL(netdev_class_remove_file_ns);
>
> +bool netdev_class_has_file_ns(const char *name, const void *ns)
> +{
> + return class_has_file_ns(&net_class, name, ns);
> +}
> +EXPORT_SYMBOL(netdev_class_has_file_ns);

Again, this feels broken, it can not solve a race condition.

greg k-h

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