[PATCH] _proc_do_string(): fix short reads
If you try to read things like /proc/sys/kernel/osrelease with single-byte
reads, you get just one byte and then EOF. This is because _proc_do_string()
assumes that the caller is read()ing into a buffer which is large enough to
fit the whole string in a single hit.
Fix.
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 84cab0c..e0ac6cd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1686,13 +1686,12 @@
size_t len;
char __user *p;
char c;
-
- if (!data || !maxlen || !*lenp ||
- (*ppos && !write)) {
+
+ if (!data || !maxlen || !*lenp) {
*lenp = 0;
return 0;
}
-
+
if (write) {
len = 0;
p = buffer;
@@ -1713,6 +1712,15 @@
len = strlen(data);
if (len > maxlen)
len = maxlen;
+
+ if (*ppos > len) {
+ *lenp = 0;
+ return 0;
+ }
+
+ data += *ppos;
+ len -= *ppos;
+
if (len > *lenp)
len = *lenp;
if (len)