On Thu, Jan 27, 2022 at 12:46 PM James Morris [off-list ref] wrote:

On Thu, 27 Jan 2022, Casey Schaufler wrote:

quoted

The usual LSM hook "bail on fail" scheme doesn't work for cases where
a security module may return an error code indicating that it does not
recognize an input.  In this particular case Smack sees a mount option
that it recognizes, and returns 0. A call to a BPF hook follows, which
returns -ENOPARAM, which confuses the caller because Smack has processed
its data.

The SELinux hook incorrectly returns 1 on success. There was a time
when this was correct, however the current expectation is that it
return 0 on success. This is repaired.

Reported-by: syzbot+d1e3b1d92d25abf97943@syzkaller.appspotmail.com
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

Acked-by: James Morris <redacted>

Looks good to me too, thanks Casey.  Since James' already ACK'd it, I
went ahead and pulled this into selinux/next.

quoted

---
 security/security.c      | 17 +++++++++++++++--
 security/selinux/hooks.c |  5 ++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/security/security.c b/security/security.c
index 3d4eb474f35b..e649c8691be2 100644
--- a/security/security.c
+++ b/security/security.c

@@ -884,9 +884,22 @@ int security_fs_context_dup(struct fs_context *fc, struct

fs_context *src_fc)
      return call_int_hook(fs_context_dup, 0, fc, src_fc);
 }

-int security_fs_context_parse_param(struct fs_context *fc, struct
fs_parameter *param)
+int security_fs_context_parse_param(struct fs_context *fc,
+                                 struct fs_parameter *param)
 {
-     return call_int_hook(fs_context_parse_param, -ENOPARAM, fc, param);
+     struct security_hook_list *hp;
+     int trc;
+     int rc = -ENOPARAM;
+
+     hlist_for_each_entry(hp, &security_hook_heads.fs_context_parse_param,
+                          list) {
+             trc = hp->hook.fs_context_parse_param(fc, param);
+             if (trc == 0)
+                     rc = 0;
+             else if (trc != -ENOPARAM)
+                     return trc;
+     }
+     return rc;
 }

 int security_sb_alloc(struct super_block *sb)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5b6895e4fc29..371f67a37f9a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c

@@ -2860,10 +2860,9 @@ static int selinux_fs_context_parse_param(struct

fs_context *fc,
              return opt;

      rc = selinux_add_opt(opt, param->string, &fc->security);
-     if (!rc) {
+     if (!rc)
              param->string = NULL;
-             rc = 1;
-     }
+
      return rc;
 }

-- 
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