From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:42512) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmcT3-0003aK-VN for qemu-devel@nongnu.org; Thu, 24 Jan 2019 05:42:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gmcT3-0001ZY-1V for qemu-devel@nongnu.org; Thu, 24 Jan 2019 05:42:41 -0500 Date: Thu, 24 Jan 2019 11:42:17 +0100 From: Kevin Wolf Message-ID: <20190124104217.GD4601@localhost.localdomain> References: <20190111164506.15971-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190111164506.15971-1-pbonzini@redhat.com> Subject: Re: [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: Paolo Bonzini Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org Am 11.01.2019 um 17:45 hat Paolo Bonzini geschrieben: > 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 though > the stores in the insertion sort are protected against overflows, the same is not > true of the reads and the final store of 0xb0. > > This basically does the same thing as commit 57dbb58d80 ("scsi-generic: avoid > 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 before. > > 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 == 0x00) { > + } else if (s->needs_vpd_bl_emulation && page == 0x00 && r->buflen >= 4) { If you make it page == 0, it would even fit in 80 characters. :-) > /* > * 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(SCSIGenericReq *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 initialization > - * 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 = lduw_be_p(r->buf + 2) + 4; > - page_idx > 4 && r->buf[page_idx - 1] >= 0xb0; > - page_idx--) { > + page_idx = lduw_be_p(r->buf + 2) + 4; > + page_idx = MIN(page_idx, r->buflen); > + while (page_idx > 4 && r->buf[page_idx - 1] >= 0xb0) { > if (page_idx < r->buflen) { > r->buf[page_idx] = r->buf[page_idx - 1]; > } > + page_idx--; > + } > + if (page_idx < r->buflen) { > + r->buf[page_idx] = 0xb0; > } > - r->buf[page_idx] = 0xb0; > stw_be_p(r->buf + 2, lduw_be_p(r->buf + 2) + 1); > } > } Looks good to me. Reviewed-by: Kevin Wolf