linux-kernel - [PATCH] apparmor: secid: fix error return value in error handling path

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Message-ID: <20180504133932.GA15968@embeddedor.com>
Date:   Fri, 4 May 2018 08:39:32 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     John Johansen <john.johansen@...onical.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>
Cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] apparmor: secid: fix error return value in error handling
 path

Currently, function apparmor_secid_to_secctx returns always zero,
no matter if the value returned by aa_label_asxprint is negative
(which implies that an error has occurred).

Fix this by temporarily storing the value returned by aa_label_asxprint
into a variable of type int (signed) for its further evaluation.

Addresses-Coverity-ID: 1468514 ("Unsigned compared against 0")
Fixes: c092921219d2 ("apparmor: add support for mapping secids and using secctxes")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 security/apparmor/secid.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c
index 5029248..4b902ed 100644
--- a/security/apparmor/secid.c
+++ b/security/apparmor/secid.c
@@ -142,6 +142,7 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
 	/* TODO: cache secctx and ref count so we don't have to recreate */
 	struct aa_label *label = aa_secid_to_label(secid);
+	int seclen_tmp;
 
 	AA_BUG(!secdata);
 	AA_BUG(!seclen);
@@ -150,17 +151,19 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 		return -EINVAL;
 
 	if (secdata)
-		*seclen = aa_label_asxprint(secdata, root_ns, label,
+		seclen_tmp = aa_label_asxprint(secdata, root_ns, label,
 					    FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
 					    FLAG_HIDDEN_UNCONFINED |
 					    FLAG_ABS_ROOT, GFP_ATOMIC);
 	else
-		*seclen = aa_label_snxprint(NULL, 0, root_ns, label,
+		seclen_tmp = aa_label_snxprint(NULL, 0, root_ns, label,
 					    FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
 					    FLAG_HIDDEN_UNCONFINED |
 					    FLAG_ABS_ROOT);
-	if (*seclen < 0)
+	if (seclen_tmp < 0)
 		return -ENOMEM;
+	else
+		*seclen = seclen_tmp;
 
 	return 0;
 }
-- 
2.7.4