proc/sysctl: add shared variables for range check

In the sysctl code the proc_dointvec_minmax() function is often used to
validate the user supplied value between an allowed range.  This
function uses the extra1 and extra2 members from struct ctl_table as
minimum and maximum allowed value.

On sysctl handler declaration, in every source file there are some
readonly variables containing just an integer which address is assigned
to the extra1 and extra2 members, so the sysctl range is enforced.

The special values 0, 1 and INT_MAX are very often used as range
boundary, leading duplication of variables like zero=0, one=1,
int_max=INT_MAX in different source files:

    $ git grep -E '\.extra[12].*&(zero|one|int_max)' |wc -l
    248

Add a const int array containing the most commonly used values, some
macros to refer more easily to the correct array member, and use them
instead of creating a local one for every object file.

This is the bloat-o-meter output comparing the old and new binary
compiled with the default Fedora config:

    # scripts/bloat-o-meter -d vmlinux.o.old vmlinux.o
    add/remove: 2/2 grow/shrink: 0/2 up/down: 24/-188 (-164)
    Data                                         old     new   delta
    sysctl_vals                                    -      12     +12
    __kstrtab_sysctl_vals                          -      12     +12
    max                                           14      10      -4
    int_max                                       16       -     -16
    one                                           68       -     -68
    zero                                         128      28    -100
    Total: Before=20583249, After=20583085, chg -0.00%

[mcroce@redhat.com: tipc: remove two unused variables]
  Link: http://lkml.kernel.org/r/20190530091952.4108-1-mcroce@redhat.com
[akpm@linux-foundation.org: fix net/ipv6/sysctl_net_ipv6.c]
[arnd@arndb.de: proc/sysctl: make firmware loader table conditional]
  Link: http://lkml.kernel.org/r/20190617130014.1713870-1-arnd@arndb.de
[akpm@linux-foundation.org: fix fs/eventpoll.c]
Link: http://lkml.kernel.org/r/20190430180111.10688-1-mcroce@redhat.com
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 15 insertions, 25 deletions

diff --git a/drivers/base/firmware_loader/fallback_table.c b/drivers/base/firmware_loader/fallback_table.c
index 776dd69cf5be..ba9d30b28edc 100644
--- a/drivers/base/firmware_loader/fallback_table.c
+++ b/drivers/base/firmware_loader/fallback_table.c
@@ -16,9 +16,6 @@
  * firmware fallback configuration table
  */
 
-static unsigned int zero;
-static unsigned int one = 1;
-
 struct firmware_fallback_config fw_fallback_config = {
 	.force_sysfs_fallback = IS_ENABLED(CONFIG_FW_LOADER_USER_HELPER_FALLBACK),
 	.loading_timeout = 60,
@@ -26,6 +23,7 @@ struct firmware_fallback_config fw_fallback_config = {
 };
 EXPORT_SYMBOL_GPL(fw_fallback_config);
 
+#ifdef CONFIG_SYSCTL
 struct ctl_table firmware_config_table[] = {
 	{
 		.procname	= "force_sysfs_fallback",
@@ -33,8 +31,8 @@ struct ctl_table firmware_config_table[] = {
 		.maxlen         = sizeof(unsigned int),
 		.mode           = 0644,
 		.proc_handler   = proc_douintvec_minmax,
-		.extra1		= &zero,
-		.extra2		= &one,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
 	},
 	{
 		.procname	= "ignore_sysfs_fallback",
@@ -42,9 +40,10 @@ struct ctl_table firmware_config_table[] = {
 		.maxlen         = sizeof(unsigned int),
 		.mode           = 0644,
 		.proc_handler   = proc_douintvec_minmax,
-		.extra1		= &zero,
-		.extra2		= &one,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
 	},
 	{ }
 };
 EXPORT_SYMBOL_GPL(firmware_config_table);
+#endif
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 3d8162d28730..a700c5c3d167 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -274,8 +274,6 @@
 #define POLL_PERIOD (NSEC_PER_SEC / POLL_FREQUENCY)
 
 /* for sysctl proc_dointvec_minmax of dev.i915.perf_stream_paranoid */
-static int zero;
-static int one = 1;
 static u32 i915_perf_stream_paranoid = true;
 
 /* The maximum exponent the hardware accepts is 63 (essentially it selects one
@@ -3366,8 +3364,8 @@ static struct ctl_table oa_table[] = {
 	 .maxlen = sizeof(i915_perf_stream_paranoid),
 	 .mode = 0644,
 	 .proc_handler = proc_dointvec_minmax,
-	 .extra1 = &zero,
-	 .extra2 = &one,
+	 .extra1 = SYSCTL_ZERO,
+	 .extra2 = SYSCTL_ONE,
 	 },
 	{
 	 .procname = "oa_max_sample_rate",
@@ -3375,7 +3373,7 @@ static struct ctl_table oa_table[] = {
 	 .maxlen = sizeof(i915_oa_max_sample_rate),
 	 .mode = 0644,
 	 .proc_handler = proc_dointvec_minmax,
-	 .extra1 = &zero,
+	 .extra1 = SYSCTL_ZERO,
 	 .extra2 = &oa_sample_rate_hard_limit,
 	 },
 	{}
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 894da5abdc55..ebd35fc35290 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1197,8 +1197,6 @@ static struct kmsg_dumper hv_kmsg_dumper = {
 };
 
 static struct ctl_table_header *hv_ctl_table_hdr;
-static int zero;
-static int one = 1;
 
 /*
  * sysctl option to allow the user to control whether kmsg data should be
@@ -1211,8 +1209,8 @@ static struct ctl_table hv_ctl_table[] = {
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec_minmax,
-		.extra1		= &zero,
-		.extra2		= &one
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE
 	},
 	{}
 };
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index fde8d4073e74..4c49f53afa3e 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -855,8 +855,6 @@ void tty_ldisc_deinit(struct tty_struct *tty)
 	tty->ldisc = NULL;
 }
 
-static int zero;
-static int one = 1;
 static struct ctl_table tty_table[] = {
 	{
 		.procname	= "ldisc_autoload",
@@ -864,8 +862,8 @@ static struct ctl_table tty_table[] = {
 		.maxlen		= sizeof(tty_ldisc_autoload),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
-		.extra1		= &zero,
-		.extra2		= &one,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
 	},
 	{ }
 };
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index d37dd5bb7a8f..37a36c6b9f93 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -77,9 +77,6 @@ static int xen_hotplug_unpopulated;
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 
-static int zero;
-static int one = 1;
-
 static struct ctl_table balloon_table[] = {
 	{
 		.procname	= "hotplug_unpopulated",
@@ -87,8 +84,8 @@ static struct ctl_table balloon_table[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1         = &zero,
-		.extra2         = &one,
+		.extra1         = SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
 	},
 	{ }
 };