linux-kernel - [PATCH v1] audit: fix illegal pointer dereference for openat2

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Date:   Wed,  9 Feb 2022 16:50:04 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Richard Guy Briggs <rgb@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Aleksa Sarai <cyphar@...har.com>,
        Arnd Bergmann <arnd@...nel.org>, stable@...r.kernel.org,
        Jeff Mahoney <jeffm@...e.com>
Subject: [PATCH v1] audit: fix illegal pointer dereference for openat2

The user pointer was being illegally dereferenced directly to get the
open_how flags data in audit_match_perm.  Use the previously saved flags
data elsewhere in the context instead.

Coverage is provided by the audit-testsuite syscalls_file test case.

Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/c96031b4-b76d-d82c-e232-1cccbbf71946@suse.com
Fixes: 1c30e3af8a79 ("audit: add support for the openat2 syscall")
Reported-by: Jeff Mahoney <jeffm@...e.com>
Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 kernel/auditsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fce5d43a933f..81ab510a7be4 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -185,7 +185,7 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
 	case AUDITSC_EXECVE:
 		return mask & AUDIT_PERM_EXEC;
 	case AUDITSC_OPENAT2:
-		return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);
+		return mask & ACC_MODE((u32)(ctx->openat2.flags));
 	default:
 		return 0;
 	}
-- 
2.27.0