[PATCH 3.16 38/61] scsi: sg: close race condition in sg_remove_sfp_usercontext()

[Ben Hutchings]

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Hannes Reinecke <hare@xxxxxxx>

commit 97d27b0dd015e980ade63fda111fd1353276e28b upstream.

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@xxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Tested-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/scsi/sg.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -561,6 +561,7 @@ 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);
@@ -601,6 +602,7 @@ 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;
 }
 
@@ -835,6 +837,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
 	if (k) {
 		SCSI_LOG_TIMEOUT(1, printk("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)) {
@@ -844,6 +847,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
 		}
 
 		sg_finish_rem_req(srp);
+		sg_remove_request(sfp, srp);
 		return -ENODEV;
 	}
 
@@ -1367,6 +1371,7 @@ 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);
 }
 
@@ -1876,8 +1881,6 @@ sg_finish_rem_req(Sg_request *srp)
 	else
 		sg_remove_scat(req_schp);
 
-	sg_remove_request(sfp, srp);
-
 	return ret;
 }
 
@@ -2211,12 +2214,17 @@ 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,