commit 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
introduced an incorrect WARN_ON_ONCE() and missed a sequence where
sg_device_destroy() was used after 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.
Drop the incorrect WARN_ON_ONCE() - allowing more than one concurrent
access to the sg device - and make sure sg_device_destroy() is not used
after scsi_device_put() in the error handling.
Link: https://lore.kernel.org/all/5375B275-D137-4D5F-BE25-6AF8ACAE41EF@xxxxxxxxxxxxx
Fixes: 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alexander Wetzel <Alexander@xxxxxxxxxxxxxx>
---
Changes compared to V1: fixed commit message
Changes compared to V2: Fix use-after free
---
drivers/scsi/sg.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 386981c6976a..baf870a03ecf 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -285,6 +285,7 @@ sg_open(struct inode *inode, struct file *filp)
int dev = iminor(inode);
int flags = filp->f_flags;
struct request_queue *q;
+ struct scsi_device *device;
Sg_device *sdp;
Sg_fd *sfp;
int retval;
@@ -301,11 +302,12 @@ sg_open(struct inode *inode, struct file *filp)
/* This driver's module count bumped by fops_get in <linux/fs.h> */
/* Prevent the device driver from vanishing while we sleep */
- retval = scsi_device_get(sdp->device);
+ device = sdp->device;
+ retval = scsi_device_get(device);
if (retval)
goto sg_put;
- retval = scsi_autopm_get_device(sdp->device);
+ retval = scsi_autopm_get_device(device);
if (retval)
goto sdp_put;
@@ -313,7 +315,7 @@ sg_open(struct inode *inode, struct file *filp)
* check if O_NONBLOCK. Permits SCSI commands to be issued
* during error recovery. Tread carefully. */
if (!((flags & O_NONBLOCK) ||
- scsi_block_when_processing_errors(sdp->device))) {
+ scsi_block_when_processing_errors(device))) {
retval = -ENXIO;
/* we are in error recovery for this device */
goto error_out;
@@ -344,7 +346,7 @@ sg_open(struct inode *inode, struct file *filp)
if (sdp->open_cnt < 1) { /* no existing opens */
sdp->sgdebug = 0;
- q = sdp->device->request_queue;
+ q = device->request_queue;
sdp->sg_tablesize = queue_max_segments(q);
}
sfp = sg_add_sfp(sdp);
@@ -370,10 +372,11 @@ sg_open(struct inode *inode, struct file *filp)
error_mutex_locked:
mutex_unlock(&sdp->open_rel_lock);
error_out:
- scsi_autopm_put_device(sdp->device);
+ scsi_autopm_put_device(device);
sdp_put:
- scsi_device_put(sdp->device);
- goto sg_put;
+ kref_put(&sdp->d_ref, sg_device_destroy);
+ scsi_device_put(device);
+ return retval;
}
/* Release resources associated with a successful sg_open()
@@ -2233,7 +2236,6 @@ sg_remove_sfp_usercontext(struct work_struct *work)
"sg_remove_sfp: sfp=0x%p\n", sfp));
kfree(sfp);
- 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);
--
2.44.0
