From: Sven Van Asbroeck <thesven73@gmail.com>
Date: Mon, 17 Jun 2019 18:23:54 +0000 (-0400)
Subject: firmware: improve LSM/IMA security behaviour
X-Git-Tag: v5.1.19~49
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f42cde4aa63d0bdb9a54c7d36cedf4c0fc5d8843;p=thirdparty%2Fkernel%2Fstable.git

firmware: improve LSM/IMA security behaviour

commit 2472d64af2d3561954e2f05365a67692bb852f2a upstream.

The firmware loader queries if LSM/IMA permits it to load firmware
via the sysfs fallback. Unfortunately, the code does the opposite:
it expressly permits sysfs fw loading if security_kernel_load_data(
LOADING_FIRMWARE) returns -EACCES. This happens because a
zero-on-success return value is cast to a bool that's true on success.

Fix the return value handling so we get the correct behaviour.

Fixes: 6e852651f28e ("firmware: add call to LSM hook before firmware sysfs fallback")
Cc: Stable <stable@vger.kernel.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index b5c865fe263b2..818d8c37d70a9 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -659,7 +659,7 @@ static bool fw_run_sysfs_fallback(enum fw_opt opt_flags)
 	/* Also permit LSMs and IMA to fail firmware sysfs fallback */
 	ret = security_kernel_load_data(LOADING_FIRMWARE);
 	if (ret < 0)
-		return ret;
+		return false;
 
 	return fw_force_sysfs_fallback(opt_flags);
 }