Commit 27df6f25 authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by J. Bruce Fields

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: default avatarVegard Nossum <>
Signed-off-by: default avatarCyrill Gorcunov <>
CC: Ingo Oeser <>
Cc: Neil Brown <>
Cc: Chuck Lever <>
Cc: Greg Banks <>
Cc: Tom Tucker <>
Signed-off-by: default avatarJ. Bruce Fields <>
parent c228c24b
......@@ -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
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