Messages in this thread | | | From | Taehee Yoo <> | Date | Sun, 5 Apr 2020 18:17:50 +0900 | Subject | Re: [PATCH net v2 2/3] net: core: add netdev_class_has_file_ns() helper function |
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On Sun, 5 Apr 2020 at 16:32, Greg KH <gregkh@linuxfoundation.org> wrote: >
Hi Greg, Thank you for the review!
> On Sun, Apr 05, 2020 at 02:18:22AM +0900, Taehee Yoo wrote: > > On Sun, 5 Apr 2020 at 00:51, Greg KH <gregkh@linuxfoundation.org> wrote: > > > > > > > Hi Greg, > > Thank you for your review! > > > > > 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. > > > > > > > This function is considered to be used under rtnl mutex and > > I assume that no one could use "/sys/class/net/*" outside of rtnl mutex. > > So, I think it returns the correct information under rtnl mutex. > > But you are creating a globally exported function that can be called > from anywhere, and as such, is not useful because it has no locking or > hints of how to use it correctly at all. >
Yes, I agree with that.
> Again, don't push this "solution" down to sysfs to solve, you know if > you have a device that is not cleaned up yet, so don't try to > rename/create a device of the same name before that is finished. >
Okay, Thank you for that. I will find another way to fix it.
Thanks a lot! Taehee Yoo
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