From 27df6f25ff218072e0e879a96beeb398a79cdbc8 Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Sun, 31 Aug 2008 19:25:49 +0400 Subject: [PATCH] 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 Signed-off-by: Cyrill Gorcunov CC: Ingo Oeser Cc: Neil Brown Cc: Chuck Lever Cc: Greg Banks Cc: Tom Tucker Signed-off-by: J. Bruce Fields --- net/sunrpc/sysctl.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c index 0f8c439b848a..5231f7aaac0e 100644 --- a/net/sunrpc/sysctl.c +++ b/net/sunrpc/sysctl.c @@ -60,24 +60,14 @@ static int proc_do_xprt(ctl_table *table, int write, struct file *file, 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 -- 2.20.1