Linux: Remove ZFS_AC_KERNEL_SRC_MODULE_PARAM_CALL_CONST autotools check

On older kernels, the definition for `module_param_call()` typecasts
function pointers to `(void *)`, which triggers -Werror, causing the
check to return false when it should return true.

Fixing this breaks the build process on some older kernels because they
define a `__check_old_set_param()` function in their headers that checks
for a non-constified `->set()`. We workaround that through the c
preprocessor by defining `__check_old_set_param(set)` to `(set)`, which
prevents the build failures.

However, it is now apparent that all kernels that we support have
adopted the GRSecurity change, so there is no need to have an explicit
autotools check for it anymore. We therefore remove the autotools check,
while adding the workaround to our headers for the build time
non-constified `->set()` check done by older kernel headers.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13984
Closes #14004

diff --git a/config/kernel-mod-param.m4 b/config/kernel-mod-param.m4
deleted file mode 100644 (file)
index e00f19d..0000000
--- a/config/kernel-mod-param.m4
+++ /dev/null
@@ -1,33 +0,0 @@
-dnl #
-dnl # Grsecurity kernel API change
-dnl # constified parameters of module_param_call() methods
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_MODULE_PARAM_CALL_CONST], [
-       ZFS_LINUX_TEST_SRC([module_param_call], [
-               #include <linux/module.h>
-               #include <linux/moduleparam.h>
-
-               int param_get(char *b, const struct kernel_param *kp)
-               {
-                       return (0);
-               }
-
-               int param_set(const char *b, const struct kernel_param *kp)
-               {
-                       return (0);
-               }
-
-               module_param_call(p, param_set, param_get, NULL, 0644);
-       ],[])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_MODULE_PARAM_CALL_CONST], [
-       AC_MSG_CHECKING([whether module_param_call() is hardened])
-       ZFS_LINUX_TEST_RESULT([module_param_call], [
-               AC_MSG_RESULT(yes)
-               AC_DEFINE(MODULE_PARAM_CALL_CONST, 1,
-                   [hardened module_param_call])
-       ],[
-               AC_MSG_RESULT(no)
-       ])
-])

diff --git a/config/kernel.m4 b/config/kernel.m4
index 6aad2cf88e0208f574027534d14aa45f5567aa8e..8a5c9296ad7ba451a84ec80044fcf27b1bc6b1f0 100644 (file)
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -122,7 +122,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
        ZFS_AC_KERNEL_SRC_FMODE_T
        ZFS_AC_KERNEL_SRC_KUIDGID_T
        ZFS_AC_KERNEL_SRC_KUID_HELPERS
-       ZFS_AC_KERNEL_SRC_MODULE_PARAM_CALL_CONST
        ZFS_AC_KERNEL_SRC_RENAME
        ZFS_AC_KERNEL_SRC_CURRENT_TIME
        ZFS_AC_KERNEL_SRC_USERNS_CAPABILITIES
@@ -243,7 +242,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
        ZFS_AC_KERNEL_FMODE_T
        ZFS_AC_KERNEL_KUIDGID_T
        ZFS_AC_KERNEL_KUID_HELPERS
-       ZFS_AC_KERNEL_MODULE_PARAM_CALL_CONST
        ZFS_AC_KERNEL_RENAME
        ZFS_AC_KERNEL_CURRENT_TIME
        ZFS_AC_KERNEL_USERNS_CAPABILITIES

diff --git a/include/os/linux/kernel/linux/mod_compat.h b/include/os/linux/kernel/linux/mod_compat.h
index a091bbfe179d46cba5af4568e642eedeb35edcad..1b15f9c6e04303ddba67f7790ab186c2a14af166 100644 (file)
--- a/include/os/linux/kernel/linux/mod_compat.h
+++ b/include/os/linux/kernel/linux/mod_compat.h
@@ -30,12 +30,16 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 
-/* Grsecurity kernel API change */
-#ifdef MODULE_PARAM_CALL_CONST
+/*
+ * Despite constifying struct kernel_param_ops, some older kernels define a
+ * `__check_old_set_param()` function in their headers that checks for a
+ * non-constified `->set()`. This has long been fixed in Linux mainline, but
+ * since we support older kernels, we workaround it by using a preprocessor
+ * definition to disable it.
+ */
+#define        __check_old_set_param(_) (0)
+
 typedef const struct kernel_param zfs_kernel_param_t;
-#else
-typedef struct kernel_param zfs_kernel_param_t;
-#endif
 
 #define        ZMOD_RW 0644
 #define        ZMOD_RD 0444