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 <[email protected]>
Signed-off-by: Cyrill Gorcunov <[email protected]>
CC: Ingo Oeser <[email protected]>
Cc: Neil Brown <[email protected]>
Cc: Chuck Lever <[email protected]>
Cc: Greg Banks <[email protected]>
Cc: Tom Tucker <[email protected]>
Signed-off-by: J. Bruce Fields <[email protected]>

0 files changed, 0 insertions, 0 deletions