Commit 8d060877 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

[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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c75fb88d
......@@ -1686,13 +1686,12 @@ static int _proc_do_string(void* data, int maxlen, int write,
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 @@ static int _proc_do_string(void* data, int maxlen, int write,
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)
......
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