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Subject[PATCH 4.18 25/44] dm mpath: fix attached_handler_name leak and dangling hw_handler_name pointer
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Mike Snitzer <snitzer@redhat.com>

commit b592211c33f745af67a3271ce77c10fc1e6d6241 upstream.

Commit e8f74a0f0011 ("dm mpath: eliminate need to use
scsi_device_from_queue") introduced 2 regressions:
1) memory leak occurs if attached_handler_name is not assigned to
m->hw_handler_name
2) m->hw_handler_name can become a dangling pointer if the
RETAIN_ATTACHED_HW_HANDLER flag is set and scsi_dh_attach() returns
-EBUSY.

Fix both of these by clearing 'attached_handler_name' pointer passed to
setup_scsi_dh() after it is assigned to m->hw_handler_name. And if
setup_scsi_dh() doesn't consume 'attached_handler_name' parse_path()
will kfree() it.

Fixes: e8f74a0f0011 ("dm mpath: eliminate need to use scsi_device_from_queue")
Cc: stable@vger.kernel.org # 4.16+
Reported-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-mpath.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -806,19 +806,19 @@ static int parse_path_selector(struct dm
}

static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
- const char *attached_handler_name, char **error)
+ const char **attached_handler_name, char **error)
{
struct request_queue *q = bdev_get_queue(bdev);
int r;

if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
retain:
- if (attached_handler_name) {
+ if (*attached_handler_name) {
/*
* Clear any hw_handler_params associated with a
* handler that isn't already attached.
*/
- if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
+ if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
kfree(m->hw_handler_params);
m->hw_handler_params = NULL;
}
@@ -830,7 +830,8 @@ retain:
* handler instead of the original table passed in.
*/
kfree(m->hw_handler_name);
- m->hw_handler_name = attached_handler_name;
+ m->hw_handler_name = *attached_handler_name;
+ *attached_handler_name = NULL;
}
}

@@ -867,7 +868,7 @@ static struct pgpath *parse_path(struct
struct pgpath *p;
struct multipath *m = ti->private;
struct request_queue *q;
- const char *attached_handler_name;
+ const char *attached_handler_name = NULL;

/* we need at least a path arg */
if (as->argc < 1) {
@@ -890,7 +891,7 @@ static struct pgpath *parse_path(struct
attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
if (attached_handler_name || m->hw_handler_name) {
INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
- r = setup_scsi_dh(p->path.dev->bdev, m, attached_handler_name, &ti->error);
+ r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
if (r) {
dm_put_device(ti, p->path.dev);
goto bad;
@@ -905,6 +906,7 @@ static struct pgpath *parse_path(struct

return p;
bad:
+ kfree(attached_handler_name);
free_pgpath(p);
return ERR_PTR(r);
}

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