Hi Ido,
On Tue, 1 Oct 2024 16:38:39 +0300, Ido Schimmel wrote:
On Tue, Oct 01, 2024 at 02:11:27PM +0200, Greg KH wrote:
On Tue, Oct 01, 2024 at 02:20:35PM +0300, Ido Schimmel wrote:
I read the stable rules and I am not providing an "upstream commit ID" since the code in upstream has been reworked, making this fix irrelevant. The only affected stable kernel is 6.1.y.
You need to document the heck out of why this is only relevant for this one specific kernel branch IN the changelog text, so that we understand what is going on, AND you need to get acks from the relevant maintainers of this area of the kernel to accept something that is not in Linus's tree.
But first of, why? Why not just take the upstrema commits instead?
There were a lot of changes as part of the 6.3 cycle to completely rework the semantics of the devlink instance reference count. As part of these changes, commit d77278196441 ("devlink: bump the instance index directly when iterating") inadvertently fixed the bug mentioned in this patch. This commit cannot be applied to 6.1.y as-is because a prior commit (also in 6.3) moved the code to a different file (leftover.c -> core.c). There might be more dependencies that I'm currently unaware of.
The alternative, proposed in this patch, is to provide a minimal and contained fix for the bug introduced in upstream commit c2368b19807a ("net: devlink: introduce "unregistering" mark and use it during devlinks iteration") as part of the 6.0 cycle.
The above explains why the patch is only relevant to 6.1.y.
Thanks for bringing up this topic!
For what it's worth, syzbot would also greatly benefit from your fix: https://github.com/google/syzkaller/issues/5328
I've built a kernel locally with your changes, run syzkaller against it, and I can confirm that the kernel no longer crashes due to devlink.