sunrpc: fix possible overrun on read of /proc/sys/sunrpc/transports
Vegard Nossum reported
----------------------
> I noticed that something weird is going on with /proc/sys/sunrpc/transports.
> This file is generated in net/sunrpc/sysctl.c, function proc_do_xprt(). When
> I "cat" this file, I get the expected output:
> $ cat /proc/sys/sunrpc/transports
> tcp 1048576
> udp 32768
> But I think that it does not check the length of the buffer supplied by
> userspace to read(). With my original program, I found that the stack was
> being overwritten by the characters above, even when the length given to
> read() was just 1.
David Wagner added (among other things) that copy_to_user could be
probably used here.
Ingo Oeser suggested to use simple_read_from_buffer() here.
The conclusion is that proc_do_xprt doesn't check for userside buffer
size indeed so fix this by using Ingo's suggestion.
Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
CC: Ingo Oeser <ioe-lkml@rameria.de>
Cc: Neil Brown <neilb@suse.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Greg Banks <gnb@sgi.com>
Cc: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c
index 0f8c439..5231f7a 100644
--- a/net/sunrpc/sysctl.c
+++ b/net/sunrpc/sysctl.c
@@ -60,24 +60,14 @@
void __user *buffer, size_t *lenp, loff_t *ppos)
{
char tmpbuf[256];
- int len;
+ size_t len;
+
if ((*ppos && !write) || !*lenp) {
*lenp = 0;
return 0;
}
- if (write)
- return -EINVAL;
- else {
- len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
- if (!access_ok(VERIFY_WRITE, buffer, len))
- return -EFAULT;
-
- if (__copy_to_user(buffer, tmpbuf, len))
- return -EFAULT;
- }
- *lenp -= len;
- *ppos += len;
- return 0;
+ len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
+ return simple_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
}
static int