On Thu, Sep 27, 2012 at 8:24 PM, Yasuaki Ishimatsu <isimatu.yasu...@jp.fujitsu.com> wrote: > Hi Chen, > > > 2012/09/27 19:20, Ni zhan Chen wrote: >> >> Hi Congyang, >> >> 2012/9/27 <we...@cn.fujitsu.com> >> >>> From: Yasuaki Ishimatsu <isimatu.yasu...@jp.fujitsu.com> >>> >>> When calling remove_memory_block(), the function shows following message >>> at >>> device_release(). >>> >>> Device 'memory528' does not have a release() function, it is broken and >>> must >>> be fixed. >>> >> >> What's the difference between the patch and original implemetation? > > > The implementation is for removing a memory_block. So the purpose is > same as original one. But original code is bad manner. kobject_cleanup() > is called by remove_memory_block() at last. But release function for > releasing memory_block is not registered. As a result, the kernel message > is shown. IMHO, memory_block should be release by the releae function.
but your patch introduced use after free bug, if i understand correctly. See unregister_memory() function. After your patch, kobject_put() call release_memory_block() and kfree(). and then device_unregister() will touch freed memory. static void unregister_memory(struct memory_block *memory) { BUG_ON(memory->dev.bus != &memory_subsys); /* drop the ref. we got in remove_memory_block() */ kobject_put(&memory->dev.kobj); device_unregister(&memory->dev); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/