From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: David Howells <dhowells@redhat.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Christoph Hellwig <hch@infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
ast@kernel.org, axboe@kernel.dk, bfields@fieldses.org,
bridge@lists.linux-foundation.org, chainsaw@gentoo.org,
christian.brauner@ubuntu.com, chuck.lever@oracle.com,
davem@davemloft.net, gregkh@linuxfoundation.org,
jarkko.sakkinen@linux.intel.com, jmorris@namei.org,
josh@joshtriplett.org, keescook@chromium.org,
keyrings@vger.kernel.org, kuba@kernel.org,
lars.ellenberg@linbit.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-security-module@vger.kernel.org,
nikolay@cumulusnetworks.com, philipp.reisner@linbit.com,
ravenexp@gmail.com, roopa@cumulusnetworks.com, serge@hallyn.com,
slyfox@gentoo.org, viro@zeniv.linux.org.uk,
yangtiezhu@loongson.cn, netdev@vger.kernel.org,
markward@linux.ibm.com, linux-s390 <linux-s390@vger.kernel.org>
Subject: Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used seems to break linux bridge on s390x (bisected)
Date: Fri, 3 Jul 2020 09:52:01 +0900 [thread overview]
Message-ID: <d8a74a06-de97-54ae-de03-0d955e82f62b@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200702194656.GV4332@42.do-not-panic.com>
On 2020/07/03 4:46, Luis Chamberlain wrote:
> On Thu, Jul 02, 2020 at 01:26:53PM +0900, Tetsuo Handa wrote:
>> On 2020/07/02 0:38, Luis Chamberlain wrote:
>>> @@ -156,6 +156,18 @@ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
>>> */
>>> if (KWIFEXITED(ret))
>>> sub_info->retval = KWEXITSTATUS(ret);
>>> + /*
>>> + * Do we really want to be passing the signal, or do we pass
>>> + * a single error code for all cases?
>>> + */
>>> + else if (KWIFSIGNALED(ret))
>>> + sub_info->retval = KWTERMSIG(ret);
>>
>> No, this is bad. Caller of usermode helper is unable to distinguish exit(9)
>> and e.g. SIGKILL'ed by the OOM-killer.
>
> Right, the question is: do we care?
Yes, we have to care.
> And the umh patch "umh: fix processed error when UMH_WAIT_PROC is used"
> changed this to:
>
> - if (ret >= 0) {
> + if (ret != 0) {
>
> Prior to the patch negative return values from userspace were still
> being captured, and likewise signals, but the error value was not
> raw, not the actual value. After the patch, since we check for ret != 0
> we still upkeep the sanity check for any error, correct the error value,
> but as you noted signals were ignored as I made the wrong assumption
> we would ignore them. The umh sub_info->retval is set after my original
> patch only if KWIFSIGNALED(ret)), and ignored signals, and so that
> would be now capitured with the additional KWIFSIGNALED(ret)) check.
"call_usermodehelper_keys() == 0" (i.e. usermode helper was successfully
started and successfully terminated via exit(0)) is different from "there is
nothing to do". call_sbin_request_key() == 0 case still has to check for
possibility of -ENOKEY case.
>
> The question still stands:
>
> Do we want to open code all these checks or simply wrap them up in
> the umh. If we do the later, as you note exit(9) and a SIGKILL will
> be the same to the inspector in the kernel. But do we care?
Yes, we do care.
>
> Do we really want umh callers differntiatin between signals and exit values?
Yes, we do.
>
> The alternative to making a compromise is using generic wrappers for
> things which make sense and letting the callers use those.
I suggest just introducing KWIFEXITED()/KWEXITSTATUS()/KWIFSIGNALED()/KWTERMSIG()
macros and fixing the callers, for some callers are not aware of possibility of
KWIFSIGNALED() case.
For example, conn_try_outdate_peer() in drivers/block/drbd/drbd_nl.c misbehaves if
drbd_usermode_helper process was terminated by a signal, for the switch() statement
after returning from conn_helper() is assuming that the return value of conn_helper()
is a KWEXITSTATUS() value if drbd_usermode_helper process was successfully started.
If drbd_usermode_helper process was terminated by SIGQUIT (which is 3),
conn_try_outdate_peer() will by error hit "case P_INCONSISTENT:" (which is 3);
conn_try_outdate_peer() should hit "default: /* The script is broken ... */"
unless KWIFEXITED() == true.
Your patch is trying to obnubilate the return code.
next prev parent reply other threads:[~2020-07-03 0:54 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 15:49 [PATCH 0/5] kmod/umh: a few fixes Luis R. Rodriguez
2020-06-10 15:49 ` [PATCH 1/5] selftests: kmod: Use variable NAME in kmod_test_0001() Luis R. Rodriguez
2020-06-10 15:49 ` [PATCH 2/5] kmod: Remove redundant "be an" in the comment Luis R. Rodriguez
2020-06-10 15:49 ` [PATCH 3/5] test_kmod: Avoid potential double free in trigger_config_run_type() Luis R. Rodriguez
2020-06-10 15:49 ` [PATCH 4/5] umh: fix processed error when UMH_WAIT_PROC is used Luis R. Rodriguez
2020-06-23 14:11 ` linux-next: umh: fix processed error when UMH_WAIT_PROC is used seems to break linux bridge on s390x (bisected) Christian Borntraeger
2020-06-23 14:23 ` Christian Borntraeger
2020-06-24 11:11 ` Christian Borntraeger
2020-06-24 12:05 ` Luis Chamberlain
2020-06-24 13:17 ` Luis Chamberlain
2020-06-24 16:13 ` Luis Chamberlain
2020-06-24 14:43 ` Christoph Hellwig
2020-06-24 15:54 ` Christian Borntraeger
2020-06-24 16:09 ` Luis Chamberlain
2020-06-24 17:58 ` Christian Borntraeger
2020-06-24 18:09 ` Christian Borntraeger
2020-06-24 18:32 ` Christian Borntraeger
2020-06-24 18:37 ` Christian Borntraeger
2020-06-25 13:26 ` Christian Borntraeger
2020-06-26 2:54 ` Luis Chamberlain
2020-06-26 5:22 ` Christian Borntraeger
2020-06-26 9:00 ` Christoph Hellwig
2020-06-26 11:40 ` Luis Chamberlain
2020-06-26 11:50 ` Luis Chamberlain
2020-06-30 17:57 ` Luis Chamberlain
2020-07-01 10:08 ` Christian Borntraeger
2020-07-01 13:24 ` Tetsuo Handa
2020-07-01 13:53 ` Luis Chamberlain
2020-07-01 14:08 ` Tetsuo Handa
2020-07-01 15:38 ` Luis Chamberlain
2020-07-01 15:48 ` Christian Borntraeger
2020-07-01 15:58 ` Luis Chamberlain
2020-07-01 16:01 ` Christian Borntraeger
2020-07-02 4:26 ` Tetsuo Handa
2020-07-02 19:46 ` Luis Chamberlain
2020-07-03 0:52 ` Tetsuo Handa [this message]
2020-07-03 13:28 ` Luis Chamberlain
2020-07-01 15:26 ` Christian Borntraeger
2020-07-01 13:46 ` Luis Chamberlain
2020-06-10 15:49 ` [PATCH 5/5] selftests: simplify kmod failure value Luis R. Rodriguez
2020-06-18 0:43 ` [PATCH 0/5] kmod/umh: a few fixes Andrew Morton
[not found] ` <20200619204626.GK11244@42.do-not-panic.com>
2020-06-19 21:07 ` Luis Chamberlain
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