[PATCHv4 6/6] sg: close race condition in sg_remove_sfp_usercontext()

[Hannes Reinecke]

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

Reported-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Hannes Reinecke <h...@suse.com>
Reviewed-by: Johannes Thumshirn <jthumsh...@suse.de>
Tested-by: Johannes Thumshirn <jthumsh...@suse.de>
---
 drivers/scsi/sg.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 5c9f1b9..8147147 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -524,6 +524,7 @@ static int sg_allow_access(struct file *filp, unsigned char 
*cmd)
        } 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);
@@ -564,6 +565,7 @@ static int sg_allow_access(struct file *filp, unsigned char 
*cmd)
        }
 err_out:
        err2 = sg_finish_rem_req(srp);
+       sg_remove_request(sfp, srp);
        return err ? : err2 ? : count;
 }
 
@@ -800,6 +802,7 @@ static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
                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)) {
@@ -810,6 +813,7 @@ static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
                }
 
                sg_finish_rem_req(srp);
+               sg_remove_request(sfp, srp);
                return -ENODEV;
        }
 
@@ -1285,6 +1289,7 @@ static long sg_compat_ioctl(struct file *filp, unsigned 
int cmd_in, unsigned lon
        struct sg_fd *sfp = srp->parentfp;
 
        sg_finish_rem_req(srp);
+       sg_remove_request(sfp, srp);
        kref_put(&sfp->f_ref, sg_remove_sfp);
 }
 
@@ -1831,8 +1836,6 @@ static long sg_compat_ioctl(struct file *filp, unsigned 
int cmd_in, unsigned lon
        else
                sg_remove_scat(sfp, req_schp);
 
-       sg_remove_request(sfp, srp);
-
        return ret;
 }
 
@@ -2177,12 +2180,17 @@ static long sg_compat_ioctl(struct file *filp, unsigned 
int cmd_in, unsigned lon
        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,
-- 
1.8.5.6