scsi: sg: Avoid sg device teardown race

commit 27f58c04a8f438078583041468ec60597841284d upstream.

sg_remove_sfp_usercontext() must not use sg_device_destroy() after calling
scsi_device_put().

sg_device_destroy() is accessing the parent scsi_device request_queue which
will already be set to NULL when the preceding call to scsi_device_put()
removed the last reference to the parent scsi_device.

The resulting NULL pointer exception will then crash the kernel.

Link: https://lore.kernel.org/r/20240305150509.23896-1-Alexander@wetzel-home.de
Fixes: db59133e9279 ("scsi: sg: fix blktrace debugfs entries leakage")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Wetzel <Alexander@wetzel-home.de>
Link: https://lore.kernel.org/r/20240320213032.18221-1-Alexander@wetzel-home.de
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0d8afffd1683b1fd6a10de3a3f18106333616be6..8bd95ee1825a6808c909bdf21d8f0ed9635e6aab 100644 (file)
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2208,6 +2208,7 @@ sg_remove_sfp_usercontext(struct work_struct *work)
 {
        struct sg_fd *sfp = container_of(work, struct sg_fd, ew.work);
        struct sg_device *sdp = sfp->parentdp;
+       struct scsi_device *device = sdp->device;
        Sg_request *srp;
        unsigned long iflags;
 
@@ -2233,8 +2234,9 @@ sg_remove_sfp_usercontext(struct work_struct *work)
                        "sg_remove_sfp: sfp=0x%p\n", sfp));
        kfree(sfp);
 
-       scsi_device_put(sdp->device);
+       WARN_ON_ONCE(kref_read(&sdp->d_ref) != 1);
        kref_put(&sdp->d_ref, sg_device_destroy);
+       scsi_device_put(device);
        module_put(THIS_MODULE);
 }