Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
+-- On Fri, 26 Oct 2018, Mark Kanda wrote --+ | Yes, please use that acknowledgement text in lieu of a 'Reported-by' line. Okay, thank you. -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
On 10/26/2018 1:37 PM, P J P wrote: +-- On Fri, 26 Oct 2018, Mark Kanda wrote --+ | Deja vu requested that we include the following text in the commit message: | | Discovered by Deja vu Security. Reported by Oracle. | | Would that be acceptable? Generally an email-id is used/preferred in the commit log message. We could use above for acknowledgement and avoid Reported-by in the commit log message if that suits Deja vu team. Please let me know your/their preference. Yes, please use that acknowledgement text in lieu of a 'Reported-by' line. Thanks, -Mark
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
+-- On Fri, 26 Oct 2018, Mark Kanda wrote --+ | Deja vu requested that we include the following text in the commit message: | | Discovered by Deja vu Security. Reported by Oracle. | | Would that be acceptable? Generally an email-id is used/preferred in the commit log message. We could use above for acknowledgement and avoid Reported-by in the commit log message if that suits Deja vu team. Please let me know your/their preference. Thank you. -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
On 10/26/2018 4:25 AM, P J P wrote: +-- On Thu, 25 Oct 2018, Ameya More wrote --+ | While Mark and I reported this issue to you, it was actually discovered by | Dejvau Security and they should receive credit for reporting this issue. | http://www.dejavusecurity.com I see; Would it be possible to share email-id of the original reporter to include in the commit log message? Deja vu requested that we include the following text in the commit message: Discovered by Deja vu Security. Reported by Oracle. Would that be acceptable? Thanks, -Mark
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
+-- On Fri, 26 Oct 2018, Paolo Bonzini wrote --+ | > -int msg_len; | > +uint8_t msg_len; | | Not wrong per se, but it's also not clear why it's needed. I understand | that you want to switch from signed to unsigned, but it is not mentioned | in the commit message. Changed to uint8_t because IIUC 'msg_len' is likely be < LSI_MAX_MSGIN_LEN=8. And uint32_t seems rather large for it. | The switch to 8-bit, and below from VMSTATE_INT32 to VMSTATE_UINT8, is | wrong because it changes the format of the live migration stream. I see. | I'm not sure it's appropriate to check for out of bounds reads here, | because if s->msg_len is greater than LSI_MAX_MSGIN_LEN, then this test | doesn't exclude you've already had an out of bounds write before. | Indeed the msg_len is checked in lsi_add_msg_byte in order to avoid out | of bounds accesses in either lsi_add_msg_byte or lsi_do_msgin. You | could assert here that the variable is in range, I guess. Okay. | However, the out of bounds s->msg_len can actually happen in one other | case: namely, if a malicious live migration stream includes a bogus | s->msg_len. Such live migration stream should be rejected; the fix for | that is to add a lsi_post_load function, point to it in | vmstate_lsi_scsi, and check there for s->msg_len <= LSI_MAX_MSGIN_LEN. Okay, sending a revised patch v1 in a bit. Thank you. -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
+-- On Thu, 25 Oct 2018, Ameya More wrote --+ | While Mark and I reported this issue to you, it was actually discovered by | Dejvau Security and they should receive credit for reporting this issue. | http://www.dejavusecurity.com I see; Would it be possible to share email-id of the original reporter to include in the commit log message? Thank you. -- Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
On 25/10/2018 22:09, P J P wrote:
> From: Prasad J Pandit
>
> While writing a message in 'lsi_do_msgin', message length value
> in msg_len could be invalid, add check to avoid OOB access issue.
>
> Reported-by: Ameya More
> Signed-off-by: Prasad J Pandit
> ---
> hw/scsi/lsi53c895a.c | 9 ++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
> index d1e6534311..a266c5a113 100644
> --- a/hw/scsi/lsi53c895a.c
> +++ b/hw/scsi/lsi53c895a.c
> @@ -205,7 +205,7 @@ typedef struct {
> /* Action to take at the end of a MSG IN phase.
> 0 = COMMAND, 1 = disconnect, 2 = DATA OUT, 3 = DATA IN. */
> int msg_action;
> -int msg_len;
> +uint8_t msg_len;
Not wrong per se, but it's also not clear why it's needed. I understand
that you want to switch from signed to unsigned, but it is not mentioned
in the commit message.
The switch to 8-bit, and below from VMSTATE_INT32 to VMSTATE_UINT8, is
wrong because it changes the format of the live migration stream.
> uint8_t msg[LSI_MAX_MSGIN_LEN];
> /* 0 if SCRIPTS are running or stopped.
> * 1 if a Wait Reselect instruction has been issued.
> @@ -861,12 +861,15 @@ static void lsi_do_status(LSIState *s)
>
> static void lsi_do_msgin(LSIState *s)
> {
> -int len;
> +uint8_t len;
> trace_lsi_do_msgin(s->dbc, s->msg_len);
> s->sfbr = s->msg[0];
> len = s->msg_len;
> if (len > s->dbc)
> len = s->dbc;
> +if (len > LSI_MAX_MSGIN_LEN) {
> +len = LSI_MAX_MSGIN_LEN;
> +}
I'm not sure it's appropriate to check for out of bounds reads here,
because if s->msg_len is greater than LSI_MAX_MSGIN_LEN, then this test
doesn't exclude you've already had an out of bounds write before.
Indeed the msg_len is checked in lsi_add_msg_byte in order to avoid out
of bounds accesses in either lsi_add_msg_byte or lsi_do_msgin. You
could assert here that the variable is in range, I guess.
However, the out of bounds s->msg_len can actually happen in one other
case: namely, if a malicious live migration stream includes a bogus
s->msg_len. Such live migration stream should be rejected; the fix for
that is to add a lsi_post_load function, point to it in
vmstate_lsi_scsi, and check there for s->msg_len <= LSI_MAX_MSGIN_LEN.
Thanks,
Paolo
> pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len);
> /* Linux drivers rely on the last byte being in the SIDL. */
> s->sidl = s->msg[len - 1];
> @@ -2114,7 +2117,7 @@ static const VMStateDescription vmstate_lsi_scsi = {
> VMSTATE_INT32(carry, LSIState),
> VMSTATE_INT32(status, LSIState),
> VMSTATE_INT32(msg_action, LSIState),
> -VMSTATE_INT32(msg_len, LSIState),
> +VMSTATE_UINT8(msg_len, LSIState),
> VMSTATE_BUFFER(msg, LSIState),
> VMSTATE_INT32(waiting, LSIState),
>
>
Re: [Qemu-devel] [PATCH] lsi53c895a: check message length value
Hi Prasad,
Thanks for following up on this. While Mark and I reported this issue to
you, it was actually discovered by Dejvau Security and they should
receive credit for reporting this issue.
http://www.dejavusecurity.com
Thanks,
Ameya
On 10/25/2018 03:09 PM, P J P wrote:
From: Prasad J Pandit
While writing a message in 'lsi_do_msgin', message length value
in msg_len could be invalid, add check to avoid OOB access issue.
Reported-by: Ameya More
Signed-off-by: Prasad J Pandit
---
hw/scsi/lsi53c895a.c | 9 ++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index d1e6534311..a266c5a113 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -205,7 +205,7 @@ typedef struct {
/* Action to take at the end of a MSG IN phase.
0 = COMMAND, 1 = disconnect, 2 = DATA OUT, 3 = DATA IN. */
int msg_action;
-int msg_len;
+uint8_t msg_len;
uint8_t msg[LSI_MAX_MSGIN_LEN];
/* 0 if SCRIPTS are running or stopped.
* 1 if a Wait Reselect instruction has been issued.
@@ -861,12 +861,15 @@ static void lsi_do_status(LSIState *s)
static void lsi_do_msgin(LSIState *s)
{
-int len;
+uint8_t len;
trace_lsi_do_msgin(s->dbc, s->msg_len);
s->sfbr = s->msg[0];
len = s->msg_len;
if (len > s->dbc)
len = s->dbc;
+if (len > LSI_MAX_MSGIN_LEN) {
+len = LSI_MAX_MSGIN_LEN;
+}
pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len);
/* Linux drivers rely on the last byte being in the SIDL. */
s->sidl = s->msg[len - 1];
@@ -2114,7 +2117,7 @@ static const VMStateDescription vmstate_lsi_scsi = {
VMSTATE_INT32(carry, LSIState),
VMSTATE_INT32(status, LSIState),
VMSTATE_INT32(msg_action, LSIState),
-VMSTATE_INT32(msg_len, LSIState),
+VMSTATE_UINT8(msg_len, LSIState),
VMSTATE_BUFFER(msg, LSIState),
VMSTATE_INT32(waiting, LSIState),
[Qemu-devel] [PATCH] lsi53c895a: check message length value
From: Prasad J Pandit
While writing a message in 'lsi_do_msgin', message length value
in msg_len could be invalid, add check to avoid OOB access issue.
Reported-by: Ameya More
Signed-off-by: Prasad J Pandit
---
hw/scsi/lsi53c895a.c | 9 ++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index d1e6534311..a266c5a113 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -205,7 +205,7 @@ typedef struct {
/* Action to take at the end of a MSG IN phase.
0 = COMMAND, 1 = disconnect, 2 = DATA OUT, 3 = DATA IN. */
int msg_action;
-int msg_len;
+uint8_t msg_len;
uint8_t msg[LSI_MAX_MSGIN_LEN];
/* 0 if SCRIPTS are running or stopped.
* 1 if a Wait Reselect instruction has been issued.
@@ -861,12 +861,15 @@ static void lsi_do_status(LSIState *s)
static void lsi_do_msgin(LSIState *s)
{
-int len;
+uint8_t len;
trace_lsi_do_msgin(s->dbc, s->msg_len);
s->sfbr = s->msg[0];
len = s->msg_len;
if (len > s->dbc)
len = s->dbc;
+if (len > LSI_MAX_MSGIN_LEN) {
+len = LSI_MAX_MSGIN_LEN;
+}
pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len);
/* Linux drivers rely on the last byte being in the SIDL. */
s->sidl = s->msg[len - 1];
@@ -2114,7 +2117,7 @@ static const VMStateDescription vmstate_lsi_scsi = {
VMSTATE_INT32(carry, LSIState),
VMSTATE_INT32(status, LSIState),
VMSTATE_INT32(msg_action, LSIState),
-VMSTATE_INT32(msg_len, LSIState),
+VMSTATE_UINT8(msg_len, LSIState),
VMSTATE_BUFFER(msg, LSIState),
VMSTATE_INT32(waiting, LSIState),
--
2.17.2
