From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:56642) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghzvs-0006Ob-6E for qemu-devel@nongnu.org; Fri, 11 Jan 2019 11:45:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghzvo-0001KR-Lo for qemu-devel@nongnu.org; Fri, 11 Jan 2019 11:45:17 -0500 From: Paolo Bonzini Date: Fri, 11 Jan 2019 17:45:06 +0100 Message-Id: <20190111164506.15971-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH] scsi-generic: avoid possible out-of-bounds access to r->buf List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Kevin Wolf Whenever the allocation length of a SCSI request is shorter than the size= of the VPD page list, page_idx is used blindly to index into r->buf. Even thoug= h the stores in the insertion sort are protected against overflows, the sam= e is not true of the reads and the final store of 0xb0. This basically does the same thing as commit 57dbb58d80 ("scsi-generic: a= void out-of-bounds access to VPD page list", 2018-11-06), except that here the allocation length can be chosen by the guest. Note that according to the= SCSI standard, the contents of the PAGE LENGTH field are not altered based on the allocation length. The code was introduced by commit 6c219fc8a1 ("scsi-generic: keep VPD page list sorted", 2018-11-06) but the overflow was already possible befo= re. Reported-by: Kevin Wolf Fixes: a71c775b24ebc664129eb1d9b4c360590353efd5 Signed-off-by: Paolo Bonzini --- hw/scsi/scsi-generic.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index 7237b4162e..42700e8897 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -182,7 +182,7 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq = *r, SCSIDevice *s) /* Also take care of the opt xfer len. */ stl_be_p(&r->buf[12], MIN_NON_ZERO(max_transfer, ldl_be_p(&r->buf[12]))); - } else if (s->needs_vpd_bl_emulation && page =3D=3D 0x00) { + } else if (s->needs_vpd_bl_emulation && page =3D=3D 0x00 && r->b= uflen >=3D 4) { /* * Now we're capable of supplying the VPD Block Limits * response if the hardware can't. Add it in the INQUIRY @@ -193,18 +193,20 @@ static void scsi_handle_inquiry_reply(SCSIGenericRe= q *r, SCSIDevice *s) * and will use it to proper setup the SCSI device. * * VPD page numbers must be sorted, so insert 0xb0 at the - * right place with an in-place insert. After the initializ= ation - * part of the for loop is executed, the device response is - * at r[0] to r[page_idx - 1]. + * right place with an in-place insert. When the while loop + * begins the device response is at r[0] to r[page_idx - 1]. */ - for (page_idx =3D lduw_be_p(r->buf + 2) + 4; - page_idx > 4 && r->buf[page_idx - 1] >=3D 0xb0; - page_idx--) { + page_idx =3D lduw_be_p(r->buf + 2) + 4; + page_idx =3D MIN(page_idx, r->buflen); + while (page_idx > 4 && r->buf[page_idx - 1] >=3D 0xb0) { if (page_idx < r->buflen) { r->buf[page_idx] =3D r->buf[page_idx - 1]; } + page_idx--; + } + if (page_idx < r->buflen) { + r->buf[page_idx] =3D 0xb0; } - r->buf[page_idx] =3D 0xb0; stw_be_p(r->buf + 2, lduw_be_p(r->buf + 2) + 1); } } --=20 2.20.1