Commit de9e007d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

sysctl: make sure to terminate strings with a NUL

This is a slightly more complete fix for the previous minimal sysctl
string fix.  It always terminates the returned string with a NUL, even
if the full result wouldn't fit in the user-supplied buffer.

The returned length is the full untruncated length, so that you can
tell when truncation has occurred.
Signed-off-by: default avatarLinus Torvalds <>
parent 35f349ee
......@@ -2192,27 +2192,32 @@ int sysctl_string(ctl_table *table, int __user *name, int nlen,
void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen, void **context)
size_t l, len;
if (!table->data || !table->maxlen)
return -ENOTDIR;
if (oldval && oldlenp) {
if (get_user(len, oldlenp))
size_t bufsize;
if (get_user(bufsize, oldlenp))
return -EFAULT;
if (len) {
l = strlen(table->data)+1;
if (len > l) len = l;
if (len >= table->maxlen)
if (bufsize) {
size_t len = strlen(table->data), copied;
/* This shouldn't trigger for a well-formed sysctl */
if (len > table->maxlen)
len = table->maxlen;
if(copy_to_user(oldval, table->data, len))
/* Copy up to a max of bufsize-1 bytes of the string */
copied = (len >= bufsize) ? bufsize - 1 : len;
if (copy_to_user(oldval, table->data, copied) ||
put_user(0, (char __user *)(oldval + copied)))
return -EFAULT;
if(put_user(len, oldlenp))
if (put_user(len, oldlenp))
return -EFAULT;
if (newval && newlen) {
len = newlen;
size_t len = newlen;
if (len > table->maxlen)
len = table->maxlen;
if(copy_from_user(table->data, newval, len))
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