On Mon, May 23, 2022 at 03:36:02PM +0200, Greg KH wrote:
On Mon, May 23, 2022 at 02:54:45PM +0200, Jason A. Donenfeld wrote:
Hi Greg, Sasha,
I think we're finally at a good point to begin backporting the work I've done on random.c during the last 6 months. I've been maintaining branches for this incrementally as code has been merged into mainline, in order to make this moment easier than otherwise.
Assuming that Linus merges my PR for 5.19 [1] today, all of these patches are (or will be in a few hours) in Linus' tree. I've tried to backport most of the general scaffolding and design of the current state of random.c, while not backporting any new features or unusual functionality changes that might invite trouble. So, for example, the backports switch to using a cryptographic hash function, but they don't have changes like warning when the cycle counter is zero, attempting to use jitter on early uses of /dev/urandom, reseeding on suspend/hibernate notifications, or the vmgenid driver. Hopefully that strikes an okay balance between getting the core backported so that fixes are backportable, but not going too far by backporting new "nice to have" but unessential features.
In this git repo [2], there are three branches: linux-5.15.y, linux-5.17.y, and linux-5.18.y, which contain backports for everything up to and including [1].
You'll probably want to backport this to earlier kernels as well. Given that there hasn't been overly much work on the rng in the last few years, it shouldn't be too hard to take my 5.15.y branch and fill in the missing pieces there to bring it back. Given how much changes, you could probably just take every random.c change for backporting to before 5.15.
There is one snag, which is that some of the work I did during the 5.17 cycle depends on crypto I added for WireGuard, which landed in 5.6. So for 5.4 and prior, that will need backports. Fortunately, I've already done this in [3], in the branch backport-5.4.y, which I've kept up to date for a few years now. This occasion might mark the perfect excuse we've been waiting for to just backport WireGuard too to 5.4 (which might make the Android work a bit easier also) :-D.
Let me know if you have any questions, and feel free to poke me on IRC. And if all of the above sounds terrible to you, and you'd rather just not take any of this into stable, I guess that's a valid path to take too.
Let me look at this later this week after we get this next round of stable kernels out. It's normally a nice calm period for the stable kernels so this might not be that bad.
I get build errors in the 5.15 and 5.10 trees when applying these patches.
Here's the 5.10 error: In file included from ../crypto/testmgr.c:32: ../include/crypto/drbg.h:139:38: error: field 'random_ready' has incomplete type 139 | struct random_ready_callback random_ready; | ^~~~~~~~~~~~
And the same error in 5.15.
So obviously I can't take them, I'm doing a simple 'make allmodconfig' build for these trees on x86-64.
For 5.18 and 5.17, wow, lots of patches, but sure, let's see what happens, I've queued them up now.
thanks,
greg k-h