Re: [PATCH] selinux: log raw contexts as untrusted strings

On Tue, Jun 11, 2019 at 4:07 AM Ondrej Mosnacek <omosnace(a)redhat.com&gt; wrote: > These strings may come from untrusted sources (e.g. file xattrs) so they > need to be properly escaped. > > Reproducer: > # setenforce 0 > # touch /tmp/test > # setfattr -n security.selinux -v 'kuřecí řízek' /tmp/test > # runcon system_u:system_r:sshd_t:s0 cat /tmp/test > (look at the generated AVCs) > > Actual result: > type=AVC [...] trawcon=kuřecí řízek > > Expected result: > type=AVC [...] trawcon=6B75C5996563C3AD20C599C3AD7A656B > > Fixes: fede148324c3 ("selinux: log invalid contexts in AVCs") > Cc: stable(a)vger.kernel.org # v5.1+ > Signed-off-by: Ondrej Mosnacek <omosnace(a)redhat.com&gt; > --- > security/selinux/avc.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) Thanks, the patch looks fine to me, but it is borderline -stable material in my opinion. I'll add it to the stable-5.2 branch, but in the future I would prefer if you left the stable marking off patches and sent a reply discussing *why* this should go to stable so we can discuss it. I realize Greg likes to pull a lot of stuff into stable, but I try to be a bit more conservative about what gets marked. Even the simplest fix can still break things :)

I'm going to start building a test kernel now with this fix, but I might hold off on sending this up to Linus for a couple of days to see if I can catch Gen Zhang's patches in the same PR. > diff --git a/security/selinux/avc.c b/security/selinux/avc.c > index 8346a4f7c5d7..a99be508f93d 100644 > --- a/security/selinux/avc.c > +++ b/security/selinux/avc.c > @@ -739,14 +739,20 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a) > rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext, > &scontext_len); > if (!rc && scontext) { > - audit_log_format(ab, " srawcon=%s", scontext); > + if (scontext_len && scontext[scontext_len - 1] == '\0') > + scontext_len--; > + audit_log_format(ab, " srawcon="); > + audit_log_n_untrustedstring(ab, scontext, scontext_len); > kfree(scontext); > } > > rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext, > &scontext_len); > if (!rc && scontext) { > - audit_log_format(ab, " trawcon=%s", scontext); > + if (scontext_len && scontext[scontext_len - 1] == '\0') > + scontext_len--; > + audit_log_format(ab, " trawcon="); > + audit_log_n_untrustedstring(ab, scontext, scontext_len); > kfree(scontext); > } > } > -- > 2.20.1 -- paul moore www.paul-moore.com