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Subject[patch 43/88] SCSI: sg: fix races with ioctl(SG_IO)
2.6.28-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tony Battersby <tonyb@cybernetics.com>

upstream commit: a2dd3b4cea335713b58996bb07b3abcde1175f47

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>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/scsi/sg.c | 39 ++++++++++++++-------------------------
1 file changed, 14 insertions(+), 25 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -189,7 +189,7 @@ static ssize_t sg_new_read(Sg_fd * sfp,
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 _
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 _

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 *fi
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);
@@ -766,18 +768,6 @@ sg_common_write(Sg_fd * sfp, Sg_request
}

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 fil
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)),
- result);
+ (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;
}



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