| Message ID | 20200404141827.26255-1-ap420073@gmail.com |
|---|---|
| State | Changes Requested |
| Delegated to: | David Miller |
| Headers | show |
| Series | net: core: avoid unexpected situation in namespace change routine | expand |
On Sat, Apr 04, 2020 at 02:18:27PM +0000, Taehee Yoo wrote: > The new helper function is to check whether the class file is existing > or not. This function will be used by networking stack to > check "/sys/class/net/*" file. > > 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: > - Implement class_has_file_ns() instead of class_find_and_get_file_ns(). > - Change headline. > - Add kernel documentation comment. > > drivers/base/class.c | 22 ++++++++++++++++++++++ > include/linux/device/class.h | 3 ++- > 2 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/class.c b/drivers/base/class.c > index bcd410e6d70a..a2f2787f6aa7 100644 > --- a/drivers/base/class.c > +++ b/drivers/base/class.c > @@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr, > sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns); > } > > +/** > + * class_has_file_ns - check whether file is existing or not > + * @cls: the compatibility class > + * @name: name to look for > + * @ns: the namespace tag to use > + */ > +bool class_has_file_ns(struct class *cls, const char *name, > + const void *ns) Why would you use this? And what happens if the file shows up, or goes away, instantly after this call is made? This feels very broken. greg k-h
On Sun, 5 Apr 2020 at 00:50, Greg KH <gregkh@linuxfoundation.org> wrote: > Hi Greg, Thank you for your review! > On Sat, Apr 04, 2020 at 02:18:27PM +0000, Taehee Yoo wrote: > > The new helper function is to check whether the class file is existing > > or not. This function will be used by networking stack to > > check "/sys/class/net/*" file. > > > > 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: > > - Implement class_has_file_ns() instead of class_find_and_get_file_ns(). > > - Change headline. > > - Add kernel documentation comment. > > > > drivers/base/class.c | 22 ++++++++++++++++++++++ > > include/linux/device/class.h | 3 ++- > > 2 files changed, 24 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/base/class.c b/drivers/base/class.c > > index bcd410e6d70a..a2f2787f6aa7 100644 > > --- a/drivers/base/class.c > > +++ b/drivers/base/class.c > > @@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr, > > sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns); > > } > > > > +/** > > + * class_has_file_ns - check whether file is existing or not > > + * @cls: the compatibility class > > + * @name: name to look for > > + * @ns: the namespace tag to use > > + */ > > +bool class_has_file_ns(struct class *cls, const char *name, > > + const void *ns) > > Why would you use this? And what happens if the file shows up, or goes > away, instantly after this call is made? > > This feels very broken. > Ah, I missed considering other usescases. If other users don't use locks, this function would return incorrect information. The problem seems to become from that this function calls kernfs_put(). Thanks a lot! Taehee Yoo
diff --git a/drivers/base/class.c b/drivers/base/class.c index bcd410e6d70a..a2f2787f6aa7 100644 --- a/drivers/base/class.c +++ b/drivers/base/class.c @@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr, sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns); } +/** + * class_has_file_ns - check whether file is existing or not + * @cls: the compatibility class + * @name: name to look for + * @ns: the namespace tag to use + */ +bool class_has_file_ns(struct class *cls, const char *name, + const void *ns) +{ + struct kernfs_node *kn = NULL; + + if (cls) { + kn = kernfs_find_and_get_ns(cls->p->subsys.kobj.sd, name, ns); + if (kn) { + kernfs_put(kn); + return true; + } + } + return false; +} +EXPORT_SYMBOL_GPL(class_has_file_ns); + static struct class *class_get(struct class *cls) { if (cls) diff --git a/include/linux/device/class.h b/include/linux/device/class.h index e8d470c457d1..b3d43658b201 100644 --- a/include/linux/device/class.h +++ b/include/linux/device/class.h @@ -209,7 +209,8 @@ extern int __must_check class_create_file_ns(struct class *class, extern void class_remove_file_ns(struct class *class, const struct class_attribute *attr, const void *ns); - +bool class_has_file_ns(struct class *cls, const char *name, + const void *ns); static inline int __must_check class_create_file(struct class *class, const struct class_attribute *attr) {
The new helper function is to check whether the class file is existing or not. This function will be used by networking stack to check "/sys/class/net/*" file. 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: - Implement class_has_file_ns() instead of class_find_and_get_file_ns(). - Change headline. - Add kernel documentation comment. drivers/base/class.c | 22 ++++++++++++++++++++++ include/linux/device/class.h | 3 ++- 2 files changed, 24 insertions(+), 1 deletion(-)