[PATCH 6.1 078/197] lsm: fix the logic in security_inode_getsecctx()

Greg Kroah-Hartman
2024-02-20T21:01:57Z

From: Ondrej Mosnacek <omosnace@redhat.com>

commit 99b817c173cd213671daecd25ca27f56b0c7c4ec upstream.

The inode_getsecctx LSM hook has previously been corrected to have
-EOPNOTSUPP instead of 0 as the default return value to fix BPF LSM
behavior. However, the call_int_hook()-generated loop in
security_inode_getsecctx() was left treating 0 as the neutral value, so
after an LSM returns 0, the loop continues to try other LSMs, and if one
of them returns a non-zero value, the function immediately returns with
said value. So in a situation where SELinux and the BPF LSMs registered
this hook, -EOPNOTSUPP would be incorrectly returned whenever SELinux
returned 0.

Fix this by open-coding the call_int_hook() loop and making it use the
correct LSM_RET_DEFAULT() value as the neutral one, similar to what
other hooks do.

Cc: stable@vger.kernel.org
Reported-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Link: https://lore.kernel.org/selinux/CAEjxPJ4ev-pasUwGx48fDhnmjBnq_Wh90jYPwRQRAqXxmOKD4Q@mail.gmail.com/
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2257983
Fixes: b36995b8609a ("lsm: fix default return value for inode_getsecctx")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/security.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

--- a/security/security.c
+++ b/security/security.c
@@ -2186,7 +2186,19 @@ EXPORT_SYMBOL(security_inode_setsecctx);

int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
{
- return call_int_hook(inode_getsecctx, -EOPNOTSUPP, inode, ctx, ctxlen);
+ struct security_hook_list *hp;
+ int rc;
+
+ /*
+ * Only one module will provide a security context.
+ */
+ hlist_for_each_entry(hp, &security_hook_heads.inode_getsecctx, list) {
+ rc = hp->hook.inode_getsecctx(inode, ctx, ctxlen);
+ if (rc != LSM_RET_DEFAULT(inode_getsecctx))
+ return rc;
+ }
+
+ return LSM_RET_DEFAULT(inode_getsecctx);
}
EXPORT_SYMBOL(security_inode_getsecctx);