Messages in this thread | | | Date | Mon, 6 Feb 2023 19:33:27 +0100 | From | David Sterba <> | Subject | Re: [PATCH] btrfs: sysfs: Handle NULL return values |
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On Sun, Feb 05, 2023 at 08:13:30AM +0100, Greg KH wrote: > On Sat, Feb 04, 2023 at 10:35:10AM -0800, Kees Cook wrote: > > Each of to_fs_info(), discard_to_fs_info(), and to_space_info() can > > return NULL values. > > The code says it could, but I really do not think that is possible at > all, especially based on the fact that there have never been any crashes > reported here. > > So the NULL returns should just be removed instead, right?
Yes. The access to any sysfs callback always implies an existing fs_info, the sysfs files are destroyed before the instance of fs_info. If the callback is slow or stuck for some reason, the removal will block due to reference counts.
> Also, to_space_info() is a macro of container_of() which can not return > NULL. > > And get_btrfs_kobj() is just odd, that probably should be fixed up as > well, that's an indication that something is wrong with the sysfs code > if anyone has to attempt to walk the whole kobject parent path :(
The get_btrfs_kobj is relatively new and more generic than the other helpers that basically hardcoded the kobj path relative to the main sysfs object.
> So while this patch might fix up the compiler warning, it's logically > not going to change anything, let's fix this properly. I can look at it > next week if someone doesn't beat me to it.
Let me have a look, I was meaning to clean up the code to use only get_btrfs_kobj. So far there was no pressing reason for that but if gcc 13 is going to warn about the checks it needs to be fixed.
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