[PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

[PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

[Lv Yunlong]

In the free_cmd error path of callee beiscsi_exec_nemb_cmd(),
nonemb_cmd->va is freed by dma_free_coherent().
As req = nonemb_cmd.va, we can see that the freed nonemb_cmd.va
is still dereferenced and used by req->ip_params.ip_record.status.

My patch uses status to replace req->ip_params.ip_record.status
to avoid the uaf.

Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/scsi/be2iscsi/be_mgmt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/be2iscsi/be_mgmt.c b/drivers/scsi/be2iscsi/be_mgmt.c
index 462717bbb5b7..f05fcea707cd 100644
--- a/drivers/scsi/be2iscsi/be_mgmt.c
+++ b/drivers/scsi/be2iscsi/be_mgmt.c
@@ -509,6 +509,7 @@ beiscsi_if_clr_ip(struct beiscsi_hba *phba,
 {
 	struct be_cmd_set_ip_addr_req *req;
 	struct be_dma_mem nonemb_cmd;
+	u32 status;
 	int rc;
 
 	rc = beiscsi_prep_nemb_cmd(phba, &nonemb_cmd, CMD_SUBSYSTEM_ISCSI,
@@ -531,11 +532,12 @@ beiscsi_if_clr_ip(struct beiscsi_hba *phba,
 	memcpy(req->ip_params.ip_record.ip_addr.subnet_mask,
 	       if_info->ip_addr.subnet_mask,
 	       sizeof(if_info->ip_addr.subnet_mask));
+	status = req->ip_params.ip_record.status;
 	rc = beiscsi_exec_nemb_cmd(phba, &nonemb_cmd, NULL, NULL, 0);
-	if (rc < 0 || req->ip_params.ip_record.status) {
+	if (rc < 0 || status) {
 		beiscsi_log(phba, KERN_INFO, BEISCSI_LOG_CONFIG,
 			    "BG_%d : failed to clear IP: rc %d status %d\n",
-			    rc, req->ip_params.ip_record.status);
+			    rc, status);
 	}
 	return rc;
 }
-- 
2.25.1

Re: [PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

[Martin K. Petersen]

Lv,

> In the free_cmd error path of callee beiscsi_exec_nemb_cmd(),
> nonemb_cmd->va is freed by dma_free_coherent().  As req =
> nonemb_cmd.va, we can see that the freed nonemb_cmd.va is still
> dereferenced and used by req->ip_params.ip_record.status.

> My patch uses status to replace req->ip_params.ip_record.status to
> avoid the uaf.

This status is captured prior to executing the command so it doesn't
actually reflect whether the operation was successful (which I believe
was the intent).

Some of the callers of beiscsi_exec_nemb_cmd() pass a response buffer
and a response length as the two last arguments. Since
beiscsi_exec_nemb_cmd() frees the command before returning, passing a
response buffer seems to be the only way to get meaningful data out.

I am not sure whether the OPCODE_COMMON_ISCSI_NTWK_MODIFY_IP_ADDR
operation returns something useful from the controller. As far as I can
tell not all operations have a response buffer defined.

My recommendation would be to add a response buffer and try to decipher
what comes back from the firmware. Also, beiscsi_if_set_ip() appears to
have the same problem as beiscsi_if_clr_ip().

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

[michael.christie]

On 6/29/21 5:02 PM, Martin K. Petersen wrote:
> 
> Lv,
> 
>> In the free_cmd error path of callee beiscsi_exec_nemb_cmd(),
>> nonemb_cmd->va is freed by dma_free_coherent().  As req =
>> nonemb_cmd.va, we can see that the freed nonemb_cmd.va is still
>> dereferenced and used by req->ip_params.ip_record.status.
> 
>> My patch uses status to replace req->ip_params.ip_record.status to
>> avoid the uaf.
> 
> This status is captured prior to executing the command so it doesn't
> actually reflect whether the operation was successful (which I believe
> was the intent).
> 
> Some of the callers of beiscsi_exec_nemb_cmd() pass a response buffer
> and a response length as the two last arguments. Since
> beiscsi_exec_nemb_cmd() frees the command before returning, passing a
> response buffer seems to be the only way to get meaningful data out.
> 
> I am not sure whether the OPCODE_COMMON_ISCSI_NTWK_MODIFY_IP_ADDR
> operation returns something useful from the controller. As far as I can
> tell not all operations have a response buffer defined.
> 
> My recommendation would be to add a response buffer and try to decipher
> what comes back from the firmware. Also, beiscsi_if_set_ip() appears to
> have the same problem as beiscsi_if_clr_ip().
> 

Hopefully the broadcom devs will chime in, but it doesn't look like we get
a response buffer. I think we just need to move the:

      dma_free_coherent(&ctrl->pdev->dev, nonemb_cmd->size,
                          nonemb_cmd->va, nonemb_cmd->dma);

to a helper and have the callers free the cmd.

Oh yeah, I guess we haven't been able to hit this bug, because
beiscsi_if_set_ip/beiscsi_if_clr_ip hasn't been run since 2013.
This patch
https://patchwork.kernel.org/project/linux-scsi/patch/20210701002559.89533-1-michael.christie@oracle.com/
allows us to be able to set the IP and hit those code paths.

[PATCH] scsi: be2iscsi: Fix a use after free in beiscsi_if_clr_ip

[Lv Yunlong]

In the free_cmd error path of callee beiscsi_exec_nemb_cmd(),
nonemb_cmd->va is freed by dma_free_coherent().
As req = nonemb_cmd.va, we can see that the freed nonemb_cmd.va
is still dereferenced and used by req->ip_params.ip_record.status.

My patch uses status to replace req->ip_params.ip_record.status
to avoid the uaf.

Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/scsi/be2iscsi/be_mgmt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/be2iscsi/be_mgmt.c b/drivers/scsi/be2iscsi/be_mgmt.c
index 0d4928567265..b93b1a8c6c81 100644
--- a/drivers/scsi/be2iscsi/be_mgmt.c
+++ b/drivers/scsi/be2iscsi/be_mgmt.c
@@ -509,6 +509,7 @@ beiscsi_if_clr_ip(struct beiscsi_hba *phba,
 {
 	struct be_cmd_set_ip_addr_req *req;
 	struct be_dma_mem nonemb_cmd;
+	u32 status;
 	int rc;
 
 	rc = beiscsi_prep_nemb_cmd(phba, &nonemb_cmd, CMD_SUBSYSTEM_ISCSI,
@@ -531,11 +532,12 @@ beiscsi_if_clr_ip(struct beiscsi_hba *phba,
 	memcpy(req->ip_params.ip_record.ip_addr.subnet_mask,
 	       if_info->ip_addr.subnet_mask,
 	       sizeof(if_info->ip_addr.subnet_mask));
+	status = req->ip_params.ip_record.status;
 	rc = beiscsi_exec_nemb_cmd(phba, &nonemb_cmd, NULL, NULL, 0);
-	if (rc < 0 || req->ip_params.ip_record.status) {
+	if (rc < 0 || status) {
 		beiscsi_log(phba, KERN_INFO, BEISCSI_LOG_CONFIG,
 			    "BG_%d : failed to clear IP: rc %d status %d\n",
-			    rc, req->ip_params.ip_record.status);
+			    rc, status);
 	}
 	return rc;
 }
-- 
2.25.1