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[SCSI] sg: fix races with ioctl(SG_IO)

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sg_io_owned needs to be set before the command is sent to the midlevel;
otherwise, a quickly-completing command may cause a different CPU
to see "srp->done == 1 && !srp->sg_io_owned", which would lead to
incorrect behavior.

Check srp->done and set srp->orphan while holding rq_list_lock to
prevent races with sg_rq_end_io().

There is no need to check sfp->closed from read/write/ioctl/poll/etc.
since the kernel guarantees that this won't happen.

The usefulness of sg_srp_done() was questionable before; now it is
definitely not needed.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Tony Battersby 2009-01-20 17:00:09 -05:00 committed by James Bottomley
parent c6517b7942
commit a2dd3b4cea
1 changed files with 14 additions and 25 deletions
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37
drivers/scsi/sg.c
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@ -189,7 +189,7 @@ static ssize_t sg_new_read(Sg_fd * sfp, char __user *buf, size_t count,
Sg_request * srp);
static ssize_t sg_new_write(Sg_fd *sfp, struct file *file,
const char __user *buf, size_t count, int blocking,
int read_only, Sg_request **o_srp);
int read_only, int sg_io_owned, Sg_request **o_srp);
static int sg_common_write(Sg_fd * sfp, Sg_request * srp,
unsigned char *cmnd, int timeout, int blocking);
static int sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer);
@ -561,7 +561,8 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
return -EFAULT;
blocking = !(filp->f_flags & O_NONBLOCK);
if (old_hdr.reply_len < 0)
return sg_new_write(sfp, filp, buf, count, blocking, 0, NULL);
return sg_new_write(sfp, filp, buf, count,
blocking, 0, 0, NULL);
if (count < (SZ_SG_HEADER + 6))
return -EIO; /* The minimum scsi command length is 6 bytes. */
@ -642,7 +643,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
static ssize_t
sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,
size_t count, int blocking, int read_only,
size_t count, int blocking, int read_only, int sg_io_owned,
Sg_request **o_srp)
{
int k;
@ -662,6 +663,7 @@ sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,
SCSI_LOG_TIMEOUT(1, printk("sg_new_write: queue full\n"));
return -EDOM;
}
srp->sg_io_owned = sg_io_owned;
hp = &srp->header;
if (__copy_from_user(hp, buf, SZ_SG_IO_HDR)) {
sg_remove_request(sfp, srp);
@ -765,18 +767,6 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp,
return 0;
}
static int
sg_srp_done(Sg_request *srp, Sg_fd *sfp)
{
unsigned long iflags;
int done;
read_lock_irqsave(&sfp->rq_list_lock, iflags);
done = srp->done;
read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return done;
}
static int
sg_ioctl(struct inode *inode, struct file *filp,
unsigned int cmd_in, unsigned long arg)
@ -809,27 +799,26 @@ sg_ioctl(struct inode *inode, struct file *filp,
return -EFAULT;
result =
sg_new_write(sfp, filp, p, SZ_SG_IO_HDR,
blocking, read_only, &srp);
blocking, read_only, 1, &srp);
if (result < 0)
return result;
srp->sg_io_owned = 1;
while (1) {
result = 0; /* following macro to beat race condition */
__wait_event_interruptible(sfp->read_wait,
(sdp->detached || sfp->closed || sg_srp_done(srp, sfp)),
(srp->done || sdp->detached),
result);
if (sdp->detached)
return -ENODEV;
if (sfp->closed)
return 0; /* request packet dropped already */
if (0 == result)
write_lock_irq(&sfp->rq_list_lock);
if (srp->done) {
srp->done = 2;
write_unlock_irq(&sfp->rq_list_lock);
break;
}
srp->orphan = 1;
write_unlock_irq(&sfp->rq_list_lock);
return result; /* -ERESTARTSYS because signal hit process */
}
write_lock_irqsave(&sfp->rq_list_lock, iflags);
srp->done = 2;
write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
result = sg_new_read(sfp, p, SZ_SG_IO_HDR, srp);
return (result < 0) ? result : 0;
}