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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Hannes Reinecke <hare@suse.com>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.4 074/134] scsi: sg: close race condition in sg_remove_sfp_usercontext()
Date:   Mon, 19 Mar 2018 19:05:57 +0100
Message-Id: <20180319171859.944040060@linuxfoundation.org>
In-Reply-To: <20180319171849.024066323@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Reinecke <hare@suse.de>


[ Upstream commit 97d27b0dd015e980ade63fda111fd1353276e28b ]

sg_remove_sfp_usercontext() is clearing any sg requests, but needs to
take 'rq_list_lock' when modifying the list.

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Tested-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/scsi/sg.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -535,6 +535,7 @@ sg_read(struct file *filp, char __user *
 	} else
 		count = (old_hdr->result == 0) ? 0 : -EIO;
 	sg_finish_rem_req(srp);
+	sg_remove_request(sfp, srp);
 	retval = count;
 free_old_hdr:
 	kfree(old_hdr);
@@ -575,6 +576,7 @@ sg_new_read(Sg_fd * sfp, char __user *bu
 	}
 err_out:
 	err2 = sg_finish_rem_req(srp);
+	sg_remove_request(sfp, srp);
 	return err ? : err2 ? : count;
 }
 
@@ -811,6 +813,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
 		SCSI_LOG_TIMEOUT(1, sg_printk(KERN_INFO, sfp->parentdp,
 			"sg_common_write: start_req err=%d\n", k));
 		sg_finish_rem_req(srp);
+		sg_remove_request(sfp, srp);
 		return k;	/* probably out of space --> ENOMEM */
 	}
 	if (atomic_read(&sdp->detaching)) {
@@ -823,6 +826,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
 		}
 
 		sg_finish_rem_req(srp);
+		sg_remove_request(sfp, srp);
 		return -ENODEV;
 	}
 
@@ -1312,6 +1316,7 @@ sg_rq_end_io_usercontext(struct work_str
 	struct sg_fd *sfp = srp->parentfp;
 
 	sg_finish_rem_req(srp);
+	sg_remove_request(sfp, srp);
 	kref_put(&sfp->f_ref, sg_remove_sfp);
 }
 
@@ -1856,8 +1861,6 @@ sg_finish_rem_req(Sg_request *srp)
 	else
 		sg_remove_scat(sfp, req_schp);
 
-	sg_remove_request(sfp, srp);
-
 	return ret;
 }
 
@@ -2204,12 +2207,17 @@ sg_remove_sfp_usercontext(struct work_st
 	struct sg_fd *sfp = container_of(work, struct sg_fd, ew.work);
 	struct sg_device *sdp = sfp->parentdp;
 	Sg_request *srp;
+	unsigned long iflags;
 
 	/* Cleanup any responses which were never read(). */
+	write_lock_irqsave(&sfp->rq_list_lock, iflags);
 	while (!list_empty(&sfp->rq_list)) {
 		srp = list_first_entry(&sfp->rq_list, Sg_request, entry);
 		sg_finish_rem_req(srp);
+		list_del(&srp->entry);
+		srp->parentfp = NULL;
 	}
+	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
 
 	if (sfp->reserve.bufflen > 0) {
 		SCSI_LOG_TIMEOUT(6, sg_printk(KERN_INFO, sdp,