From: Paul Moore <paul@paul-moore.com>
To: Jeff Mahoney <jeffm@suse.com>, Richard Guy Briggs <rgb@redhat.com>
Cc: Linux-Audit Mailing List <linux-audit@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, Eric Paris <eparis@parisplace.org>,
Steve Grubb <sgrubb@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Eric Paris <eparis@redhat.com>, Tony Jones <tonyj@suse.de>
Subject: Re: [PATCH v4 2/3] audit: add support for the openat2 syscall
Date: Wed, 9 Feb 2022 10:57:15 -0500 [thread overview]
Message-ID: <CAHC9VhSHJwwG_3yy4bqNUuFAz87wFU8W-dGYfsoGBG786heTNg@mail.gmail.com> (raw)
In-Reply-To: <c96031b4-b76d-d82c-e232-1cccbbf71946@suse.com>
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.
--
paul-moore.com
next prev parent reply other threads:[~2022-02-09 15:57 UTC|newest]
Thread overview: 20+ 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
2021-05-19 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 [this message]
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
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
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