From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pengfei Wang , Michael Holzheu , Martin Schwidefsky , Juerg Haefliger Subject: [PATCH 4.4 158/192] s390/sclp_ctl: fix potential information leak with /dev/sclp Date: Mon, 12 Sep 2016 19:01:07 +0200 Message-Id: <20160912152205.685540864@linuxfoundation.org> In-Reply-To: <20160912152158.855601725@linuxfoundation.org> References: <20160912152158.855601725@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Martin Schwidefsky commit 532c34b5fbf1687df63b3fcd5b2846312ac943c6 upstream. The sclp_ctl_ioctl_sccb function uses two copy_from_user calls to retrieve the sclp request from user space. The first copy_from_user fetches the length of the request which is stored in the first two bytes of the request. The second copy_from_user gets the complete sclp request, but this copies the length field a second time. A malicious user may have changed the length in the meantime. Reported-by: Pengfei Wang Reviewed-by: Michael Holzheu Signed-off-by: Martin Schwidefsky Signed-off-by: Juerg Haefliger Signed-off-by: Greg Kroah-Hartman --- drivers/s390/char/sclp_ctl.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/drivers/s390/char/sclp_ctl.c +++ b/drivers/s390/char/sclp_ctl.c @@ -56,6 +56,7 @@ static int sclp_ctl_ioctl_sccb(void __us { struct sclp_ctl_sccb ctl_sccb; struct sccb_header *sccb; + unsigned long copied; int rc; if (copy_from_user(&ctl_sccb, user_area, sizeof(ctl_sccb))) @@ -65,14 +66,15 @@ static int sclp_ctl_ioctl_sccb(void __us sccb = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA); if (!sccb) return -ENOMEM; - if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sizeof(*sccb))) { + copied = PAGE_SIZE - + copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), PAGE_SIZE); + if (offsetof(struct sccb_header, length) + + sizeof(sccb->length) > copied || sccb->length > copied) { rc = -EFAULT; goto out_free; } - if (sccb->length > PAGE_SIZE || sccb->length < 8) - return -EINVAL; - if (copy_from_user(sccb, u64_to_uptr(ctl_sccb.sccb), sccb->length)) { - rc = -EFAULT; + if (sccb->length < 8) { + rc = -EINVAL; goto out_free; } rc = sclp_sync_request(ctl_sccb.cmdw, sccb);