Messages in this thread Patch in this message | | | From | zhangfeionline@gmail ... | Subject | [PATCH] driver core: Fix possible use after free on name | Date | Sun, 5 Apr 2020 09:05:49 -0700 |
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From: PengfeiZhang <zhangfeionline@gmail.com>
__class_create() copies the pointer to the name passed as an argument only to be used later. But there's a chance the caller could immediately free the passed string(e.g., local variable). This could trigger a use after free when we use class name(e.g., dev_uevent_name()called by device_destroy(),class_create_release()).
To be on the safe side: duplicate the string with kstrdup_const() so that if an unaware user passes an address to a stack-allocated buffer, we won't get the arbitrary name and crash.
Signed-off-by: PengfeiZhang <zhangfeionline@gmail.com> --- drivers/base/class.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/base/class.c b/drivers/base/class.c index bcd410e..770b3b3 100644 --- a/drivers/base/class.c +++ b/drivers/base/class.c @@ -206,6 +206,7 @@ void class_unregister(struct class *cls) static void class_create_release(struct class *cls) { pr_debug("%s called for %s\n", __func__, cls->name); + kfree_const(cls->name); kfree(cls); } @@ -227,7 +228,10 @@ struct class *__class_create(struct module *owner, const char *name, struct lock_class_key *key) { struct class *cls; - int retval; + int retval = -EINVAL; + + if (!name) + goto done; cls = kzalloc(sizeof(*cls), GFP_KERNEL); if (!cls) { @@ -235,18 +239,27 @@ struct class *__class_create(struct module *owner, const char *name, goto error; } + name = kstrdup_const(name, GFP_KERNEL); + if (!name) { + retval = -ENOMEM; + goto error; + } + cls->name = name; cls->owner = owner; cls->class_release = class_create_release; retval = __class_register(cls, key); if (retval) - goto error; + goto error_class_register; return cls; +error_class_register: + kfree(cls->name); error: kfree(cls); +done: return ERR_PTR(retval); } EXPORT_SYMBOL_GPL(__class_create); -- 2.7.4
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