linux-kernel - [PATCH 4.19 52/93] scsi: ch: Make it possible to open a ch device multiple times again

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Message-Id: <20191027203301.239747148@linuxfoundation.org>
Date:   Sun, 27 Oct 2019 22:01:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hannes Reinecke <hare@...e.de>,
        Rob Turk <robtu@...st.nl>,
        Bart Van Assche <bvanassche@....org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Subject: [PATCH 4.19 52/93] scsi: ch: Make it possible to open a ch device multiple times again

From: Bart Van Assche <bvanassche@....org>

commit 6a0990eaa768dfb7064f06777743acc6d392084b upstream.

Clearing ch->device in ch_release() is wrong because that pointer must
remain valid until ch_remove() is called. This patch fixes the following
crash the second time a ch device is opened:

BUG: kernel NULL pointer dereference, address: 0000000000000790
RIP: 0010:scsi_device_get+0x5/0x60
Call Trace:
 ch_open+0x4c/0xa0 [ch]
 chrdev_open+0xa2/0x1c0
 do_dentry_open+0x13a/0x380
 path_openat+0x591/0x1470
 do_filp_open+0x91/0x100
 do_sys_open+0x184/0x220
 do_syscall_64+0x5f/0x1a0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 085e56766f74 ("scsi: ch: add refcounting")
Cc: Hannes Reinecke <hare@...e.de>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20191009173536.247889-1-bvanassche@acm.org
Reported-by: Rob Turk <robtu@...st.nl>
Suggested-by: Rob Turk <robtu@...st.nl>
Signed-off-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/scsi/ch.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/scsi/ch.c
+++ b/drivers/scsi/ch.c
@@ -578,7 +578,6 @@ ch_release(struct inode *inode, struct f
 	scsi_changer *ch = file->private_data;

 	scsi_device_put(ch->device);
-	ch->device = NULL;
 	file->private_data = NULL;
 	kref_put(&ch->ref, ch_destroy);
 	return 0;