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* [PATCH bpf] security: Fix hook iteration for secid_to_secctx
@ 2020-05-20 12:56 KP Singh
  2020-05-20 15:15 ` Casey Schaufler
  2020-06-19 12:49 ` Ondrej Mosnacek
  0 siblings, 2 replies; 9+ messages in thread
From: KP Singh @ 2020-05-20 12:56 UTC (permalink / raw)
  To: linux-kernel, bpf, linux-security-module
  Cc: Alexei Starovoitov, Daniel Borkmann, James Morris, Anders Roxell,
	Casey Schaufler

From: KP Singh <kpsingh@google.com>

secid_to_secctx is not stackable, and since the BPF LSM registers this
hook by default, the call_int_hook logic is not suitable which
"bails-on-fail" and casues issues when other LSMs register this hook and
eventually breaks Audit.

In order to fix this, directly iterate over the security hooks instead
of using call_int_hook as suggested in:

https: //lore.kernel.org/bpf/9d0eb6c6-803a-ff3a-5603-9ad6d9edfc00@schaufler-ca.com/#t

Fixes: 98e828a0650f ("security: Refactor declaration of LSM hooks")
Fixes: 625236ba3832 ("security: Fix the default value of secid_to_secctx hook"
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: KP Singh <kpsingh@google.com>
---
 security/security.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/security/security.c b/security/security.c
index 7fed24b9d57e..51de970fbb1e 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1965,8 +1965,20 @@ EXPORT_SYMBOL(security_ismaclabel);
 
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
-	return call_int_hook(secid_to_secctx, -EOPNOTSUPP, secid, secdata,
-				seclen);
+	struct security_hook_list *hp;
+	int rc;
+
+	/*
+	 * Currently, only one LSM can implement secid_to_secctx (i.e this
+	 * LSM hook is not "stackable").
+	 */
+	hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) {
+		rc = hp->hook.secid_to_secctx(secid, secdata, seclen);
+		if (rc != LSM_RET_DEFAULT(secid_to_secctx))
+			return rc;
+	}
+
+	return LSM_RET_DEFAULT(secid_to_secctx);
 }
 EXPORT_SYMBOL(security_secid_to_secctx);
 
-- 
2.26.2.761.g0e0b3e54be-goog


^ permalink raw reply	[flat|nested] 9+ messages in thread

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Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-20 12:56 [PATCH bpf] security: Fix hook iteration for secid_to_secctx KP Singh
2020-05-20 15:15 ` Casey Schaufler
2020-05-21  1:35   ` Alexei Starovoitov
2020-05-21  2:02     ` James Morris
2020-05-21  3:12       ` Alexei Starovoitov
2020-06-19 12:49 ` Ondrej Mosnacek
2020-06-19 13:13   ` KP Singh
2020-06-19 14:16     ` Ondrej Mosnacek
2020-06-21 21:54       ` KP Singh

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