This problem was originally tracked down by Brad Spengler. When calling wireless ioctls, if a driver does not correctly validate/shrink iwp->length, the resulting copy_to_user can leak up to 64K of kernel heap contents. It seems that this is triggerable[1] in 2.6.32 at least on ath5k, but I was not able to track down how. The twisty maze of ioctl handlers stumped me. :) Other drivers I checked did not appear to have any problems, but the potential remains. I'm not sure if this patch is the right approach; it was fixed differently[2] in grsecurity. [1] http://forums.grsecurity.net/viewtopic.php?f=3&t=2290&start=0 [2] http://grsecurity.net/~spender/wireless-infoleak-fix2.patch Reported-by: Brad Spengler <spender@xxxxxxxxxxxxxx> Signed-off-by: Kees Cook <kees.cook@xxxxxxxxxxxxx> --- include/net/iw_handler.h | 1 - net/wireless/wext-core.c | 26 ++------------------------ 2 files changed, 2 insertions(+), 25 deletions(-) diff --git a/include/net/iw_handler.h b/include/net/iw_handler.h index 3afdb21..6c81f29 100644 --- a/include/net/iw_handler.h +++ b/include/net/iw_handler.h @@ -277,7 +277,6 @@ #define IW_DESCR_FLAG_EVENT 0x0002 /* Generate an event on SET */ #define IW_DESCR_FLAG_RESTRICT 0x0004 /* GET : request is ROOT only */ /* SET : Omit payload from generated iwevent */ -#define IW_DESCR_FLAG_NOMAX 0x0008 /* GET : no limit on request size */ /* Driver level flags */ #define IW_DESCR_FLAG_WAIT 0x0100 /* Wait for driver event */ diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c index 0ef17bc..55b1fd9 100644 --- a/net/wireless/wext-core.c +++ b/net/wireless/wext-core.c @@ -82,7 +82,6 @@ static const struct iw_ioctl_description standard_ioctl[] = { .header_type = IW_HEADER_TYPE_POINT, .token_size = sizeof(struct iw_priv_args), .max_tokens = 16, - .flags = IW_DESCR_FLAG_NOMAX, }, [IW_IOCTL_IDX(SIOCSIWSTATS)] = { .header_type = IW_HEADER_TYPE_NULL, @@ -134,7 +133,6 @@ static const struct iw_ioctl_description standard_ioctl[] = { .token_size = sizeof(struct sockaddr) + sizeof(struct iw_quality), .max_tokens = IW_MAX_AP, - .flags = IW_DESCR_FLAG_NOMAX, }, [IW_IOCTL_IDX(SIOCSIWSCAN)] = { .header_type = IW_HEADER_TYPE_POINT, @@ -146,7 +144,6 @@ static const struct iw_ioctl_description standard_ioctl[] = { .header_type = IW_HEADER_TYPE_POINT, .token_size = 1, .max_tokens = IW_SCAN_MAX_DATA, - .flags = IW_DESCR_FLAG_NOMAX, }, [IW_IOCTL_IDX(SIOCSIWESSID)] = { .header_type = IW_HEADER_TYPE_POINT, @@ -737,28 +734,9 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd, return -EFAULT; /* Save user space buffer size for checking */ user_length = iwp->length; - - /* Don't check if user_length > max to allow forward - * compatibility. The test user_length < min is - * implied by the test at the end. - */ - - /* Support for very large requests */ - if ((descr->flags & IW_DESCR_FLAG_NOMAX) && - (user_length > descr->max_tokens)) { - /* Allow userspace to GET more than max so - * we can support any size GET requests. - * There is still a limit : -ENOMEM. - */ - extra_size = user_length * descr->token_size; - - /* Note : user_length is originally a __u16, - * and token_size is controlled by us, - * so extra_size won't get negative and - * won't overflow... - */ - } } + /* Support for very large requests */ + extra_size = max(extra_size, iwp->length * descr->token_size); /* kzalloc() ensures NULL-termination for essid_compat. */ extra = kzalloc(extra_size, GFP_KERNEL); -- 1.7.1 -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
