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From 86e5aca7fa2927060839f3e3b40c8bd65a7e8d1e Mon Sep 17 00:00:00 2001
From: Gen Zhang <blackgod016574@gmail.com>
Date: Thu, 30 May 2019 09:10:30 +0800
Subject: scsi: mpt3sas_ctl: fix double-fetch bug in _ctl_ioctl_main()

In _ctl_ioctl_main(), 'ioctl_header' is fetched the first time from
userspace. 'ioctl_header.ioc_number' is then checked. The legal result is
saved to 'ioc'. Then, in condition MPT3COMMAND, the whole struct is fetched
again from the userspace. Then _ctl_do_mpt_command() is called, 'ioc' and
'karg' as inputs.

However, a malicious user can change the 'ioc_number' between the two
fetches, which will cause a potential security issues.  Moreover, a
malicious user can provide a valid 'ioc_number' to pass the check in first
fetch, and then modify it in the second fetch.

To fix this, we need to recheck the 'ioc_number' in the second fetch.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
Acked-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 drivers/scsi/mpt3sas/mpt3sas_ctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
index b2bb47c14d35..5181c03e82a6 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
@@ -2319,6 +2319,10 @@ _ctl_ioctl_main(struct file *file, unsigned int cmd, void __user *arg,
 			break;
 		}
 
+		if (karg.hdr.ioc_number != ioctl_header.ioc_number) {
+			ret = -EINVAL;
+			break;
+		}
 		if (_IOC_SIZE(cmd) == sizeof(struct mpt3_ioctl_command)) {
 			uarg = arg;
 			ret = _ctl_do_mpt_command(ioc, karg, &uarg->mf);
-- 
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