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[PATCH] _proc_do_string(): fix short reads

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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>
This commit is contained in:
Oleg Nesterov 2007-02-10 01:46:38 -08:00 committed by Linus Torvalds
parent c75fb88dbc
commit 8d06087714
1 changed files with 12 additions and 4 deletions
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16
kernel/sysctl.c
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@ -1686,13 +1686,12 @@ static int _proc_do_string(void* data, int maxlen, int write,
size_t len; size_t len;
char __user *p; char __user *p;
char c; char c;
if (!data || !maxlen || !*lenp || if (!data || !maxlen || !*lenp) {
(*ppos && !write)) {
*lenp = 0; *lenp = 0;
return 0; return 0;
} }
if (write) { if (write) {
len = 0; len = 0;
p = buffer; p = buffer;
@ -1713,6 +1712,15 @@ static int _proc_do_string(void* data, int maxlen, int write,
len = strlen(data); len = strlen(data);
if (len > maxlen) if (len > maxlen)
len = maxlen; len = maxlen;
if (*ppos > len) {
*lenp = 0;
return 0;
}
data += *ppos;
len -= *ppos;
if (len > *lenp) if (len > *lenp)
len = *lenp; len = *lenp;
if (len) if (len)