From 8d06087714b78e8921bd30b5c64202fe80c47339 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 10 Feb 2007 01:46:38 -0800 Subject: [PATCH] [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" Cc: Michael Tokarev Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sysctl.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 84cab0ce44d9..e0ac6cd79fcf 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -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) -- 2.20.1