From b499e5249eb80e4a7e71cfd04c6f628abdb27498 Mon Sep 17 00:00:00 2001 From: =?utf8?q?J=C3=B6rn=20Engel?= Date: Tue, 24 Apr 2012 16:13:11 -0400 Subject: [PATCH] [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: Joern Engel Acked-by: Douglas Gilbert Signed-off-by: James Bottomley --- drivers/scsi/sg.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 4a00364445f0..8e15c448a761 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -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] */ @@ -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); -- 2.20.1