On Wed, Jun 17, 2020 at 05:43:48PM -0700, Andrew Morton
wrote:> On Wed, 10 Jun 2020 15:49:18 +0000 "Luis R. Rodriguez" <mcgrof
at kernel.org> wrote:
>
> > Tiezhu Yang had sent out a patch set with a slew of kmod selftest
> > fixes, and one patch which modified kmod to return 254 when a module
> > was not found. This opened up pandora's box about why that was
being
> > used for and low and behold its because when UMH_WAIT_PROC is used
> > we call a kernel_wait4() call but have never unwrapped the error code.
> > The commit log for that fix details the rationale for the approach
> > taken. I'd appreciate some review on that, in particular nfs folks
> > as it seems a case was never really hit before.
> >
> > This goes boot tested, selftested with kmod, and 0-day gives its
> > build blessings.
>
> Any thoughts on which kernel version(s) need some/all of these fixes?
Well, in so far as fixes, this is the real important part:
* request_module() used to fail with an error code of
256 when a module was not found. Now it properly
returns 1.
* fs/nfsd/nfs4recover.c: we never were disabling the
upcall as the error code of -ENOENT or -EACCES was
*never* properly checked for error code
Since the request_module() fix is only affecting userspace
for the kmod tests, through the kmod test driver, ie, we don't expose
this to userspace in any other place, I don't see that as critical.
Let me be clear, we have a test_kmod driver which exposes knobs
and one of the knobs lets userspace query the return value of a
request_module() call, and we use this test_kmod driver to stress
test kmod loader. Let us also recall that the fix is *iff* an error
*did* occur. I *cannot* think of a reason why this would be critical
to merge to older stable kernels for this reason for request_module()'s
sake.
Bruce, Chuck:
But... for NFS... I'd like the NFS folks to really look at that
and tell us is some folks really should care about that. I also
find it perplexing there was a comment in place there to *ensure*
the error was checked for, and so it seemed someone cared for that
condition.
> > drivers/block/drbd/drbd_nl.c | 20 +++++------
> > fs/nfsd/nfs4recover.c | 2 +-
> > include/linux/sched/task.h | 13 ++++++++
> > kernel/kmod.c | 5 ++-
> > kernel/umh.c | 4 +--
> > lib/test_kmod.c | 2 +-
> > net/bridge/br_stp_if.c | 10 ++----
> > security/keys/request_key.c | 2 +-
> > tools/testing/selftests/kmod/kmod.sh | 50
+++++++++++++++++++++++-----
>
> I'm not really sure who takes kmod changes - I'll grab these unless
> someone shouts at me.
Greg usually takes it, but as usual, thanks for picking up the slack ;)
Luis