Re: [syzbot] [audit?] general protection fault in smack_log_callback
From: Paul Moore
Date: Thu Sep 19 2024 - 12:05:49 EST
On Thu, Sep 19, 2024 at 9:23 AM syzbot
<syzbot+044fdf24e96093584232@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: bdf56c7580d2 Merge tag 'slab-for-6.12' of git://git.kernel..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12584b00580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4540f5bcdd31e3de
> dashboard link: https://syzkaller.appspot.com/bug?extid=044fdf24e96093584232
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=155cffc7980000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ad24a9980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/cec9f3c675f1/disk-bdf56c75.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/21e06ae5b159/vmlinux-bdf56c75.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/1e936c954b8b/bzImage-bdf56c75.xz
>
> The issue was bisected to:
>
> commit 5f8d28f6d7d568dbbc8c5bce94894474c07afd4f
> Author: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> Date: Wed Jul 10 21:32:26 2024 +0000
>
> lsm: infrastructure management of the key security blob
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1124d69f980000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=1324d69f980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1524d69f980000
I just posted a patch which I believe should fix the problem, but I'd
like to get Casey's ACK on it before submitting upstream as it does
touch Smack code; lore link below:
https://lore.kernel.org/linux-security-module/20240919155740.29539-2-paul@xxxxxxxxxxxxxx
... in the meantime, I'm attaching the patch here so syzbot can verify
that it solves the problem.
#syz test
--
paul-moore.com
selinux,smack: properly reference the LSM blob in security_watch_key()
From: Paul Moore <paul@xxxxxxxxxxxxxx>
Unfortunately when we migrated the lifecycle management of the key LSM
blob to the LSM framework we forgot to convert the security_watch_key()
callbacks for SELinux and Smack. This patch corrects this by making use
of the selinux_key() and smack_key() helper functions respectively.
This patch also removes some input checking in the Smack callback as it
is no longer needed.
Reported-by: syzbot+044fdf24e96093584232@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 5f8d28f6d7d5 ("lsm: infrastructure management of the key security blob")
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
---
security/selinux/hooks.c | 2 +-
security/smack/smack_lsm.c | 13 +++----------
2 files changed, 4 insertions(+), 11 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 81fbfa5b80d4..67baa487cf7a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6720,7 +6720,7 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
#ifdef CONFIG_KEY_NOTIFICATIONS
static int selinux_watch_key(struct key *key)
{
- struct key_security_struct *ksec = key->security;
+ struct key_security_struct *ksec = selinux_key(key);
u32 sid = current_sid();
return avc_has_perm(sid, ksec->sid, SECCLASS_KEY, KEY__VIEW, NULL);
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index da0c2bffbd08..563fb404f659 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4629,16 +4629,9 @@ static int smack_watch_key(struct key *key)
{
struct smk_audit_info ad;
struct smack_known *tkp = smk_of_current();
+ struct smack_known **blob = smack_key(key);
int rc;
- if (key == NULL)
- return -EINVAL;
- /*
- * If the key hasn't been initialized give it access so that
- * it may do so.
- */
- if (key->security == NULL)
- return 0;
/*
* This should not occur
*/
@@ -4653,8 +4646,8 @@ static int smack_watch_key(struct key *key)
ad.a.u.key_struct.key = key->serial;
ad.a.u.key_struct.key_desc = key->description;
#endif
- rc = smk_access(tkp, key->security, MAY_READ, &ad);
- rc = smk_bu_note("key watch", tkp, key->security, MAY_READ, rc);
+ rc = smk_access(tkp, *blob, MAY_READ, &ad);
+ rc = smk_bu_note("key watch", tkp, *blob, MAY_READ, rc);
return rc;
}
#endif /* CONFIG_KEY_NOTIFICATIONS */