path: root/fs/proc/proc_sysctl.c
diff options
authorMatteo Croce <>2019-07-18 15:58:50 -0700
committerLinus Torvalds <>2019-07-18 17:08:07 -0700
commiteec4844fae7c033a0c1fc1eb3b8517aeb8b6cc49 (patch)
treea7da379423835a85c020e116a43bea6acf3c9ace /fs/proc/proc_sysctl.c
parent371096949f0ad3950b06729989bd27de51b8c5f5 (diff)
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% [ tipc: remove two unused variables] Link: [ fix net/ipv6/sysctl_net_ipv6.c] [ proc/sysctl: make firmware loader table conditional] Link: [ fix fs/eventpoll.c] Link: Signed-off-by: Matteo Croce <> Signed-off-by: Arnd Bergmann <> Acked-by: Kees Cook <> Reviewed-by: Aaron Tomlin <> Cc: Matthew Wilcox <> Cc: Stephen Rothwell <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'fs/proc/proc_sysctl.c')
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 36ad1b0d6259..d80989b6c344 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -22,6 +22,10 @@ static const struct inode_operations proc_sys_inode_operations;
static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
+/* shared constants to be used in various sysctls */
+const int sysctl_vals[] = { 0, 1, INT_MAX };
/* Support for permanently empty directories */
struct ctl_table sysctl_mount_point[] = {