Date: Wed, 11 Sep 2024 17:02:11 +0200 From: Kristof Provost <kp@FreeBSD.org> To: Mark Johnston <markj@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: f08247fd888e - main - Assert that mbufs are writable if we write to them Message-ID: <ED0A74EE-FB1B-44E6-8DEE-E34D22953825@FreeBSD.org> In-Reply-To: <ZuGtGHm-u4QiJGUz@nuc> References: <202409111118.48BBIQ2h065089@gitrepo.freebsd.org> <ZuGtGHm-u4QiJGUz@nuc>
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On 11 Sep 2024, at 16:45, Mark Johnston wrote: > On Wed, Sep 11, 2024 at 11:18:26AM +0000, Kristof Provost wrote: >> The branch main has been updated by kp: >> >> URL: https://cgit.FreeBSD.org/src/commit/?id=3Df08247fd888e6f7db0ecf2a= aa39377144ac40b4c >> >> commit f08247fd888e6f7db0ecf2aaa39377144ac40b4c >> Author: Kristof Provost <kp@FreeBSD.org> >> AuthorDate: 2024-09-10 20:15:31 +0000 >> Commit: Kristof Provost <kp@FreeBSD.org> >> CommitDate: 2024-09-11 11:17:48 +0000 >> >> Assert that mbufs are writable if we write to them >> >> m_copyback() modifies the mbuf, so it must be a writable mbuf. > > This change still triggers a panic for me when running KTLS tests. I > note that EXTPG mbufs always have M_RDONLY set, but I'm not quite sure > why. I suspect such mbufs need special handling with respect to the ne= w > assertion. > > syzbot also triggered this panic: > https://syzkaller.appspot.com/bug?extid=3D58c918369f9dc323409d > Yeah, I saw that one before I went out for a bike ride. Clearly something is wrong. Either ktls is using read-only buffers or the= M_WRITABLE() macro isn=E2=80=99t quite smart enough to spot this specifi= c case. I=E2=80=99m not familiar enough with ktls to easily tell which. I=E2=80=99ll back this assertion change out for now, so we=E2=80=99re not= panicing test machines while we figure this out. Best regards, Kristof
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