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).

Notice that *seclen* is of type u32 (32 bits, unsigned), and a less-than-zero comparison of an unsigned value is never true.

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 <[email protected]>

---
Changes is v2:
- Update changelog.
- Fix misaligned lines.

 security/apparmor/secid.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

security/apparmor/secid.c +14 -9

index 5029248..efaa0d9 100644
@@ -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 +151,21 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 		return -EINVAL;
 
 	if (secdata)
-		*seclen = aa_label_asxprint(secdata, root_ns, label,
-					    FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
-					    FLAG_HIDDEN_UNCONFINED |
-					    FLAG_ABS_ROOT, GFP_ATOMIC);
+		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,
-					    FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
-					    FLAG_HIDDEN_UNCONFINED |
-					    FLAG_ABS_ROOT);
-	if (*seclen < 0)
+		seclen_tmp = aa_label_snxprint(NULL, 0, root_ns, label,
+					       FLAG_SHOW_MODE |
+					       FLAG_VIEW_SUBNS |
+					       FLAG_HIDDEN_UNCONFINED |
+					       FLAG_ABS_ROOT);
+	if (seclen_tmp < 0)
 		return -ENOMEM;
+	else
+		*seclen = seclen_tmp;
 
 	return 0;
 }

Hi Gustavo,

if you are using the coverity scan bug tracking, please can you mark a bug as being worked on by yourself so I don't work on it at the same time as we're duplicating work here.