From 88f16db7a2fa63b9242e8a0fbc40d51722f2e2f9 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 13 May 2009 12:04:30 +0200 Subject: wext: verify buffer size for SIOCSIWENCODEEXT Another design flaw in wireless extensions (is anybody surprised?) in the way it handles the iw_encode_ext structure: The structure is part of the 'extra' memory but contains the key length explicitly, instead of it just being the length of the extra buffer - size of the struct and using the explicit key length only for the get operation (which only writes it). Therefore, we have this layout: extra: +-------------------------+ | struct iw_encode_ext { | | ... | | u16 key_len; | | u8 key[0]; | | }; | +-------------------------+ | key material | +-------------------------+ Now, all drivers I checked use ext->key_len without checking that both key_len and the struct fit into the extra buffer that has been copied from userspace. This leads to a buffer overrun while reading that buffer, depending on the driver it may be possible to specify arbitrary key_len or it may need to be a proper length for the key algorithm specified. Thankfully, this is only exploitable by root, but root can actually cause a segfault or use kernel memory as a key (which you can even get back with siocgiwencode or siocgiwencodeext from the key buffer). Fix this by verifying that key_len fits into the buffer along with struct iw_encode_ext. Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- net/wireless/wext.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'net/wireless/wext.c') diff --git a/net/wireless/wext.c b/net/wireless/wext.c index cb6a5bb85d8..0e59f9ae9b8 100644 --- a/net/wireless/wext.c +++ b/net/wireless/wext.c @@ -786,6 +786,13 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd, err = -EFAULT; goto out; } + + if (cmd == SIOCSIWENCODEEXT) { + struct iw_encode_ext *ee = (void *) extra; + + if (iwp->length < sizeof(*ee) + ee->key_len) + return -EFAULT; + } } err = handler(dev, info, (union iwreq_data *) iwp, extra); -- cgit v1.2.3-70-g09d2