linux-kernel - [PATCH] apparmor: fix off-by-one comparison on MAXMAPPED

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Date:   Tue, 22 Aug 2017 22:58:32 +0100
From:   Colin King <colin.king@...onical.com>
To:     John Johansen <john.johansen@...onical.com>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] apparmor: fix off-by-one comparison on MAXMAPPED_SIG

From: Colin Ian King <colin.king@...onical.com>

There is a an off-by-one comparision on sig against MAXMAPPED_SIG
that can lead to a read outside the sig_map array if sig
is MAXMAPPED_SIG. Fix this.

Detected with cppcheck:
"Either the condition 'sig<=35' is redundant or the array 'sig_map[35]'
is accessed at index 35, which is out of bounds."

Fixes: c6bf1adaecaa ("apparmor: add the ability to mediate signals")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 security/apparmor/ipc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/apparmor/ipc.c b/security/apparmor/ipc.c
index 66fb9ede9447..5091c78062e4 100644
--- a/security/apparmor/ipc.c
+++ b/security/apparmor/ipc.c
@@ -128,7 +128,7 @@ static inline int map_signal_num(int sig)
 		return SIGUNKNOWN;
 	else if (sig >= SIGRTMIN)
 		return sig - SIGRTMIN + 128;	/* rt sigs mapped to 128 */
-	else if (sig <= MAXMAPPED_SIG)
+	else if (sig < MAXMAPPED_SIG)
 		return sig_map[sig];
 	return SIGUNKNOWN;
 }
-- 
2.14.1