From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:40820) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Rpk2E-0005bW-6k for qemu-devel@nongnu.org; Tue, 24 Jan 2012 12:19:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Rpk27-0001Qy-8m for qemu-devel@nongnu.org; Tue, 24 Jan 2012 12:19:54 -0500 Date: Tue, 24 Jan 2012 12:19:44 -0500 From: Thomas Higdon Message-ID: <20120124171944.GD14494@akamai.com> References: <20120123171525.GM32632@akamai.com> <4F1EB7BF.8070104@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F1EB7BF.8070104@redhat.com> Subject: [Qemu-devel] [PATCH] scsi: Guard against buflen exceeding req->cmd.xfer in scsi_disk_emulate_command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: "qemu-trivial@nongnu.org" , "qemu-devel@nongnu.org" , "paul@codesourcery.com" On Tue, Jan 24, 2012 at 08:53:03AM -0500, Kevin Wolf wrote: > Am 23.01.2012 18:15, schrieb Thomas Higdon: > > This prevents the emulated SCSI device from trying to DMA more bytes to the > > initiator than are expected. Without this, the SCRIPTS code in the emulated LSI > > device eventually raises a DMA interrupt for a data overrun when an INQUIRY > > command whose buflen exceeds req->cmd.xfer is processed. It's the > > responsibility of the client to provide a request buffer and allocation > > length that are large enough for the result of the command. > > > > Signed-off-by: Thomas Higdon > > --- > > hw/scsi-disk.c | 3 +++ > > 1 files changed, 3 insertions(+), 0 deletions(-) > > > > diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c > > index 5d8bf53..71fe2a3 100644 > > --- a/hw/scsi-disk.c > > +++ b/hw/scsi-disk.c > > @@ -477,6 +477,9 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf) > > "buffer size %zd\n", page_code, req->cmd.xfer); > > return -1; > > } > > + if (buflen > req->cmd.xfer) { > > + buflen = req->cmd.xfer; > > + } > > /* done with EVPD */ > > return buflen; > > } > > I wonder if it would make sense to make this check in a more central > place like scsi_send_command(). This way we would avoid similar bugs in > other commands. Limit the return value (corresponding to the length of the buffer to be DMAed back to the intiator) to the value in req->cmd.xfer, which is the amount of data that the initiator expects. Eliminate now-duplicate code that does this guarding in the functions for individual commands. Without this, the SCRIPTS code in the emulated LSI device eventually raises a DMA interrupt for a data overrun when an INQUIRY command whose buflen exceeds req->cmd.xfer is processed. It's the responsibility of the client to provide a request buffer and allocation length that are large enough for the result of the command. Signed-off-by: Thomas Higdon --- I agree that it's better to get this into a more general place. However, I wasn't willing to pull the MIN statement up into scsi_send_command because I don't understand the interplay between 'len' in that function and r->iov.iov_len. I couldn't see that there was a general relationship between these two variables that applied to both read/write commands and other commands. hw/scsi-disk.c | 10 +--------- 1 files changed, 1 insertions(+), 9 deletions(-) diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c index 5d8bf53..11cfe73 100644 --- a/hw/scsi-disk.c +++ b/hw/scsi-disk.c @@ -391,9 +391,6 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf) } l = strlen(s->serial); - if (l > req->cmd.xfer) { - l = req->cmd.xfer; - } if (l > 20) { l = 20; } @@ -1002,9 +999,6 @@ static int scsi_disk_emulate_mode_sense(SCSIDiskReq *r, uint8_t *outbuf) outbuf[0] = ((buflen - 2) >> 8) & 0xff; outbuf[1] = (buflen - 2) & 0xff; } - if (buflen > r->req.cmd.xfer) { - buflen = r->req.cmd.xfer; - } return buflen; } @@ -1038,9 +1032,6 @@ static int scsi_disk_emulate_read_toc(SCSIRequest *req, uint8_t *outbuf) default: return -1; } - if (toclen > req->cmd.xfer) { - toclen = req->cmd.xfer; - } return toclen; } @@ -1251,6 +1242,7 @@ static int scsi_disk_emulate_command(SCSIDiskReq *r) scsi_check_condition(r, SENSE_CODE(INVALID_OPCODE)); return -1; } + buflen = MIN(buflen, req->cmd.xfer); return buflen; not_ready: -- 1.7.0.4