Commit b499e524 authored by Jörn Engel's avatar Jörn Engel Committed by James Bottomley
Browse files

[SCSI] sg: protect sdp->exclude 



Changes since v1: set_exclude now returns the new value, which gets
rid of the comma expression and the operator precedence bug.  Thanks
to Douglas for spotting it.

sdp->exclude was previously protected by the BKL.  The sg_mutex, which
replaced the BKL, only semi-protected it, as it was missing from
sg_release() and sg_proc_seq_show_debug().  Take an explicit spinlock
for it.

Signed-off-by: default avatarJoern Engel <joern@logfs.org>
Acked-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 6acddc5e

drivers/scsi/sg.c

+30 −7
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ static int sg_add(struct device *, struct class_interface *); 
static void sg_remove(struct device *, struct class_interface *);



static DEFINE_MUTEX(sg_mutex);

static DEFINE_SPINLOCK(sg_open_exclusive_lock);



static DEFINE_IDR(sg_index_idr);

static DEFINE_RWLOCK(sg_index_lock);	/* Also used to lock
@@ -173,7 +174,8 @@ typedef struct sg_device { /* holds the state of each scsi generic device */ 
	u32 index;		/* device index number */

	struct list_head sfds;

	volatile char detached;	/* 0->attached, 1->detached pending removal */

	volatile char exclude;	/* opened for exclusive access */

	/* exclude protected by sg_open_exclusive_lock */

	char exclude;		/* opened for exclusive access */

	char sgdebug;		/* 0->off, 1->sense, 9->dump dev, 10-> all devs */

	struct gendisk *disk;

	struct cdev * cdev;	/* char_dev [sysfs: /sys/cdev/major/sg<n>] */
@@ -221,6 +223,27 @@ static int sg_allow_access(struct file *filp, unsigned char *cmd) 
	return blk_verify_command(cmd, filp->f_mode & FMODE_WRITE);

}



static int get_exclude(Sg_device *sdp)

{

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&sg_open_exclusive_lock, flags);

	ret = sdp->exclude;

	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);

	return ret;

}



static int set_exclude(Sg_device *sdp, char val)

{

	unsigned long flags;



	spin_lock_irqsave(&sg_open_exclusive_lock, flags);

	sdp->exclude = val;

	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);

	return val;

}



static int

sg_open(struct inode *inode, struct file *filp)

{
@@ -269,17 +292,17 @@ sg_open(struct inode *inode, struct file *filp) 
			goto error_out;

		}

		res = wait_event_interruptible(sdp->o_excl_wait,

					   ((!list_empty(&sdp->sfds) || sdp->exclude) ? 0 : (sdp->exclude = 1)));

					   ((!list_empty(&sdp->sfds) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));

		if (res) {

			retval = res;	/* -ERESTARTSYS because signal hit process */

			goto error_out;

		}

	} else if (sdp->exclude) {	/* some other fd has an exclusive lock on dev */

	} else if (get_exclude(sdp)) {	/* some other fd has an exclusive lock on dev */

		if (flags & O_NONBLOCK) {

			retval = -EBUSY;

			goto error_out;

		}

		res = wait_event_interruptible(sdp->o_excl_wait, !sdp->exclude);

		res = wait_event_interruptible(sdp->o_excl_wait, !get_exclude(sdp));

		if (res) {

			retval = res;	/* -ERESTARTSYS because signal hit process */

			goto error_out;
@@ -298,7 +321,7 @@ sg_open(struct inode *inode, struct file *filp) 
		filp->private_data = sfp;

	else {

		if (flags & O_EXCL) {

			sdp->exclude = 0;	/* undo if error */

			set_exclude(sdp, 0);	/* undo if error */

			wake_up_interruptible(&sdp->o_excl_wait);

		}

		retval = -ENOMEM;
@@ -329,7 +352,7 @@ sg_release(struct inode *inode, struct file *filp) 
		return -ENXIO;

	SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));



	sdp->exclude = 0;

	set_exclude(sdp, 0);

	wake_up_interruptible(&sdp->o_excl_wait);



	scsi_autopm_put_device(sdp->device);
@@ -2606,7 +2629,7 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v) 
			     scsidp->lun,

			     scsidp->host->hostt->emulated);

		seq_printf(s, " sg_tablesize=%d excl=%d\n",

			   sdp->sg_tablesize, sdp->exclude);

			   sdp->sg_tablesize, get_exclude(sdp));

		sg_proc_debug_helper(s, sdp);

	}

	read_unlock_irqrestore(&sg_index_lock, iflags);

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