[Qemu-devel] [PATCH] scsi: megasas: check request object in MegasasCmd

[Qemu-devel] [PATCH] scsi: megasas: check request object in MegasasCmd

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

When processing completed commands, if SCSIRequest object
'cmd->req' was null, it could lead to null pointer dereference
in megasas_complete_command. Add check to avoid it.

Reported-by: Zhangyanyu <zyy4013@stu.ouc.edu.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/scsi/megasas.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
index 84b8caf..25e3541 100644
--- a/hw/scsi/megasas.c
+++ b/hw/scsi/megasas.c
@@ -580,9 +580,11 @@ static void megasas_complete_command(MegasasCmd *cmd)
     cmd->iov_size = 0;
     cmd->iov_offset = 0;
 
-    cmd->req->hba_private = NULL;
-    scsi_req_unref(cmd->req);
-    cmd->req = NULL;
+    if (cmd->req) {
+        cmd->req->hba_private = NULL;
+        scsi_req_unref(cmd->req);
+        cmd->req = NULL;
+    }
 
     megasas_unmap_frame(cmd->state, cmd);
     megasas_complete_frame(cmd->state, cmd->context);
-- 
2.9.3

Re: [Qemu-devel] [PATCH] scsi: megasas: check request object in MegasasCmd

[Paolo Bonzini]

On 10/05/2017 13:13, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> When processing completed commands, if SCSIRequest object
> 'cmd->req' was null, it could lead to null pointer dereference
> in megasas_complete_command. Add check to avoid it.
> 
> Reported-by: Zhangyanyu <zyy4013@stu.ouc.edu.cn>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>

What version was this reported for?  It should be fixed in v2.8.0 and
newer by commit 9e55d58806 ("megasas: clean up and fix request
completion/cancellation", 2016-11-28).

Thanks,

Paolo

Re: [Qemu-devel] [PATCH] scsi: megasas: check request object in MegasasCmd

[P J P]

  Hello Paolo,

+-- On Wed, 10 May 2017, Paolo Bonzini wrote --+
| What version was this reported for?  It should be fixed in v2.8.0 and
| newer by commit 9e55d58806 ("megasas: clean up and fix request
| completion/cancellation", 2016-11-28).

I checked the reproducer against current upstream git, it does work. IIUC, the 
above commit appears to have introduced the issue.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F