wenyang.linux@xxxxxxxxxxx writes:Thank you. While developing a driver recently, we accidentally discovered some redundant code related to extra1/extra2, so we tried to optimize it a bit.
From: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Since these static variables (ue_zero and ue_int_max) are only used for
boundary checks and will not be changed, remove it and use the ones in
our shared const array.
What happened to the plans to kill the shared const array?
You can still save a lot more by turning .extra1 and .extra2
into longs instead of keeping them as pointers and needing
constants to be pointed at somewhere.
As I recall the last version of this actually broke the code,
(but not on little endian).
This one if the constants are properly named looks better
than that, but I don't see any reason why you want shared
constants for such a handful of things. Especially when
it has proven to be error prone in the past.
The only people I can see who find a significant benefit by
consolidating all of the constants into one place are people who know
how to stomp kernel memory.
Signed-off-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Joel Granados <j.granados@xxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
kernel/ucount.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 4aa6166cb856..05bbba02ae4f 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -58,17 +58,14 @@ static struct ctl_table_root set_root = {
.permissions = set_permissions,
};
-static long ue_zero = 0;
-static long ue_int_max = INT_MAX;
-
#define UCOUNT_ENTRY(name) \
{ \
.procname = name, \
.maxlen = sizeof(long), \
.mode = 0644, \
.proc_handler = proc_doulongvec_minmax, \
- .extra1 = &ue_zero, \
- .extra2 = &ue_int_max, \
+ .extra1 = SYSCTL_LONG_ZERO, \
+ .extra2 = SYSCTL_LONG_S32_MAX, \
}
static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_user_namespaces"),