From: Paul Moore <paul@paul-moore.com>
To: Richard Guy Briggs <rgb@redhat.com>
Cc: Tony Jones <tonyj@suse.de>, Jeff Mahoney <jeffm@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
Eric Paris <eparis@redhat.com>,
Linux-Audit Mailing List <linux-audit@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Eric Paris <eparis@parisplace.org>
Subject: Re: [PATCH v4 2/3] audit: add support for the openat2 syscall
Date: Wed, 9 Feb 2022 17:29:21 -0500 [thread overview]
Message-ID: <CAHC9VhRaenJq65nUKjU6U+wFJ5HJU6Qq0Yf4ejwfNyrKEP30Lw@mail.gmail.com> (raw)
In-Reply-To: <20220209214048.GF1708086@madcap2.tricolour.ca>
On Wed, Feb 9, 2022 at 4:41 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> On 2022-02-09 10:57, Paul Moore wrote:
> > On Tue, Feb 8, 2022 at 10:44 PM Jeff Mahoney <jeffm@suse.com> wrote:
> > >
> > > Hi Richard -
> > >
> > > On 5/19/21 16:00, Richard Guy Briggs wrote:
> > > > The openat2(2) syscall was added in kernel v5.6 with commit fddb5d430ad9
> > > > ("open: introduce openat2(2) syscall")
> > > >
> > > > Add the openat2(2) syscall to the audit syscall classifier.
> > > >
> > > > Link: https://github.com/linux-audit/audit-kernel/issues/67
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > > > Link: https://lore.kernel.org/r/f5f1a4d8699613f8c02ce762807228c841c2e26f.1621363275.git.rgb@redhat.com
> > > > ---
> > >
> > > [...]
> > >
> > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > > index d775ea16505b..3f59ab209dfd 100644
> > > > --- a/kernel/auditsc.c
> > > > +++ b/kernel/auditsc.c
> > > > @@ -76,6 +76,7 @@
> > > > #include <linux/fsnotify_backend.h>
> > > > #include <uapi/linux/limits.h>
> > > > #include <uapi/linux/netfilter/nf_tables.h>
> > > > +#include <uapi/linux/openat2.h>
> > > >
> > > > #include "audit.h"
> > > >
> > > > @@ -196,6 +197,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
> > > > return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND);
> > > > case AUDITSC_EXECVE:
> > > > return mask & AUDIT_PERM_EXEC;
> > > > + case AUDITSC_OPENAT2:
> > > > + return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);
> > > > default:
> > > > return 0;
> > > > }
> > >
> > > ctx->argv[2] holds a userspace pointer and can't be dereferenced like this.
> > >
> > > I'm getting oopses, like so:
> > > BUG: unable to handle page fault for address: 00007fff961bbe70
> >
> > Thanks Jeff.
> >
> > Yes, this is obviously the wrong thing to being doing; I remember
> > checking to make sure we placed the audit_openat2_how() hook after the
> > open_how was copied from userspace, but I missed the argv dereference
> > in the syscall exit path when reviewing the code.
> >
> > Richard, as we are already copying the open_how info into
> > audit_context::openat2 safely, the obvious fix is to convert
> > audit_match_perm() to use the previously copied value instead of argv.
> > If you can't submit a patch for this today please let me know.
>
> Agreed. It would have been more awkward with the original order of the
> patches.
>
> The syscalls_file test in the audit-testsuite should have caught this.
> https://github.com/rgbriggs/audit-testsuite/commit/1c99021ae27ea23eccce2bb1861df4c9c665cd5b
> The test provided does essentially the same thing.
I would have thought so, but I've now run this multiple times on both
affected and patched kernels but I don't see the page fault on my test
system.
Anyway, that test has now been merged with the audit-testsuite as well
as some cleanup on top to test for the new OPENAT2 record when
applicable.
--
paul-moore.com
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next prev parent reply other threads:[~2022-02-09 22:29 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 20:00 [PATCH v4 0/3] audit: add support for openat2 Richard Guy Briggs
2021-05-19 20:00 ` [PATCH v4 1/3] audit: replace magic audit syscall class numbers with macros Richard Guy Briggs
2021-05-20 7:50 ` Christian Brauner
2021-08-05 22:01 ` Paul Moore
2021-09-30 20:38 ` Paul Moore
2021-10-01 19:53 ` Richard Guy Briggs
2021-10-01 20:34 ` Paul Moore
2021-10-04 15:34 ` Paul Moore
2021-05-19 20:00 ` [PATCH v4 2/3] audit: add support for the openat2 syscall Richard Guy Briggs
2021-05-20 7:58 ` Christian Brauner
2021-05-24 23:04 ` Paul Moore
2022-02-09 3:44 ` Jeff Mahoney
2022-02-09 15:57 ` Paul Moore
2022-02-09 21:18 ` Paul Moore
2022-02-09 22:13 ` Richard Guy Briggs
2022-02-09 22:31 ` Paul Moore
2022-02-09 21:40 ` Richard Guy Briggs
2022-02-09 22:29 ` Paul Moore [this message]
2021-05-19 20:00 ` [PATCH v4 3/3] audit: add OPENAT2 record to list how Richard Guy Briggs
2021-05-20 8:03 ` Christian Brauner
2021-05-24 23:08 ` Paul Moore
2021-05-25 15:00 ` Richard Guy Briggs
2021-10-04 16:08 ` Paul Moore
2021-10-04 18:27 ` Richard Guy Briggs
2021-10-21 19:00 ` Steve Grubb
2021-10-21 19:44 ` Richard Guy Briggs
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