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    Subject[PATCH 4.4 074/134] scsi: sg: close race condition in sg_remove_sfp_usercontext()
    Date
    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,

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