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Subject[PATCH] sysctl_{,ms_}jiffies: fix oldlen semantics
currently it's
1) if *oldlenp == 0,
don't writeback anything

2) if *oldlenp >= table->maxlen,
don't writeback more than table->maxlen bytes and rewrite *oldlenp
don't look at underlying type granularity

3) if 0 < *oldlenp < table->maxlen,
*cough*
string sysctls don't writeback more than *oldlenp bytes.
OK, that's because sizeof(char) == 1

int sysctls writeback anything in (0, table->maxlen] range
Though accept integers divisible by sizeof(int) for writing.

sysctl_jiffies and sysctl_ms_jiffies don't writeback anything but
sizeof(int), which violates 1) and 2).

So, make sysctl_jiffies and sysctl_ms_jiffies accept
a) *oldlenp == 0, not doing writeback
b) *oldlenp >= sizeof(int), writing one integer.

-EINVAL still returned for *oldlenp == 1, 2, 3.

Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
---

kernel/sysctl.c | 44 ++++++++++++++++++++++++++++----------------
1 file changed, 28 insertions(+), 16 deletions(-)

--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2752,17 +2752,23 @@ int sysctl_jiffies(ctl_table *table, int
void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen, void **context)
{
- if (oldval) {
+ if (oldval && oldlenp) {
size_t olen;
- if (oldlenp) {
- if (get_user(olen, oldlenp))
+
+ if (get_user(olen, oldlenp))
+ return -EFAULT;
+ if (olen) {
+ int val;
+
+ if (olen < sizeof(int))
+ return -EINVAL;
+
+ val = *(int *)(table->data) / HZ;
+ if (put_user(val, (int __user *)oldval))
+ return -EFAULT;
+ if (put_user(sizeof(int), oldlenp))
return -EFAULT;
- if (olen!=sizeof(int))
- return -EINVAL;
}
- if (put_user(*(int *)(table->data)/HZ, (int __user *)oldval) ||
- (oldlenp && put_user(sizeof(int),oldlenp)))
- return -EFAULT;
}
if (newval && newlen) {
int new;
@@ -2780,17 +2786,23 @@ int sysctl_ms_jiffies(ctl_table *table,
void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen, void **context)
{
- if (oldval) {
+ if (oldval && oldlenp) {
size_t olen;
- if (oldlenp) {
- if (get_user(olen, oldlenp))
+
+ if (get_user(olen, oldlenp))
+ return -EFAULT;
+ if (olen) {
+ int val;
+
+ if (olen < sizeof(int))
+ return -EINVAL;
+
+ val = jiffies_to_msecs(*(int *)(table->data));
+ if (put_user(val, (int __user *)oldval))
+ return -EFAULT;
+ if (put_user(sizeof(int), oldlenp))
return -EFAULT;
- if (olen!=sizeof(int))
- return -EINVAL;
}
- if (put_user(jiffies_to_msecs(*(int *)(table->data)), (int __user *)oldval) ||
- (oldlenp && put_user(sizeof(int),oldlenp)))
- return -EFAULT;
}
if (newval && newlen) {
int new;
-
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