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[SCSI] sg: protect sdp->exclude

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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: Joern Engel <joern@logfs.org>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Jörn Engel 2012-04-24 16:13:11 -04:00 committed by James Bottomley
parent 6acddc5e91
commit b499e5249e
1 changed files with 30 additions and 7 deletions
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37
drivers/scsi/sg.c
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@ -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);