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Subject[patch 5/6] ide: fix races in handling of user-space SET XFER commands
Date
From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Subject: [PATCH] ide: fix races in handling of user-space SET XFER commands

* Make cmd->tf_flags field 'u16' and add IDE_TFLAG_SET_XFER taskfile flag.

* Update ide_finish_cmd() to set xfer / re-read id if the new flag is set.

* Convert set_xfer_rate() (write handler for /proc/ide/hd?/current_speed)
and ide_cmd_ioctl() (HDIO_DRIVE_CMD ioctl handler) to use the new flag.

* Remove no longer needed disable_irq_nosync() + enable_irq() from
ide_config_drive_speed().

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
These races are easily triggable (i.e. 'hdparm -Xmode' results in the "bad
status" error during ide_driveid_update() phase) and I was no longer able to
reproduce them with this patch applied.

drivers/ide/ide-ioctls.c | 8 ++------
drivers/ide/ide-iops.c | 10 ----------
drivers/ide/ide-proc.c | 10 ++--------
drivers/ide/ide-taskfile.c | 9 ++++++++-
include/linux/ide.h | 3 ++-
5 files changed, 14 insertions(+), 26 deletions(-)

Index: b/drivers/ide/ide-ioctls.c
===================================================================
--- a/drivers/ide/ide-ioctls.c
+++ b/drivers/ide/ide-ioctls.c
@@ -166,6 +166,8 @@ static int ide_cmd_ioctl(ide_drive_t *dr
err = -EINVAL;
goto abort;
}
+
+ cmd.tf_flags |= IDE_TFLAG_SET_XFER;
}

err = ide_raw_taskfile(drive, &cmd, buf, args[3]);
@@ -173,12 +175,6 @@ static int ide_cmd_ioctl(ide_drive_t *dr
args[0] = tf->status;
args[1] = tf->error;
args[2] = tf->nsect;
-
- if (!err && xfer_rate) {
- /* active-retuning-calls future */
- ide_set_xfer_rate(drive, xfer_rate);
- ide_driveid_update(drive);
- }
abort:
if (copy_to_user((void __user *)arg, &args, 4))
err = -EFAULT;
Index: b/drivers/ide/ide-iops.c
===================================================================
--- a/drivers/ide/ide-iops.c
+++ b/drivers/ide/ide-iops.c
@@ -363,14 +363,6 @@ int ide_config_drive_speed(ide_drive_t *
* this point (lost interrupt).
*/

- /*
- * FIXME: we race against the running IRQ here if
- * this is called from non IRQ context. If we use
- * disable_irq() we hang on the error path. Work
- * is needed.
- */
- disable_irq_nosync(hwif->irq);
-
udelay(1);
tp_ops->dev_select(drive);
SELECT_MASK(drive, 1);
@@ -394,8 +386,6 @@ int ide_config_drive_speed(ide_drive_t *

SELECT_MASK(drive, 0);

- enable_irq(hwif->irq);
-
if (error) {
(void) ide_dump_status(drive, "set_drive_speed_status", stat);
return error;
Index: b/drivers/ide/ide-proc.c
===================================================================
--- a/drivers/ide/ide-proc.c
+++ b/drivers/ide/ide-proc.c
@@ -195,7 +195,6 @@ ide_devset_get(xfer_rate, current_speed)
static int set_xfer_rate (ide_drive_t *drive, int arg)
{
struct ide_cmd cmd;
- int err;

if (arg < XFER_PIO_0 || arg > XFER_UDMA_6)
return -EINVAL;
@@ -206,14 +205,9 @@ static int set_xfer_rate (ide_drive_t *d
cmd.tf.nsect = (u8)arg;
cmd.valid.out.tf = IDE_VALID_FEATURE | IDE_VALID_NSECT;
cmd.valid.in.tf = IDE_VALID_NSECT;
+ cmd.tf_flags = IDE_TFLAG_SET_XFER;

- err = ide_no_data_taskfile(drive, &cmd);
-
- if (!err) {
- ide_set_xfer_rate(drive, (u8) arg);
- ide_driveid_update(drive);
- }
- return err;
+ return ide_no_data_taskfile(drive, &cmd);
}

ide_devset_rw(current_speed, xfer_rate);
Index: b/drivers/ide/ide-taskfile.c
===================================================================
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -322,10 +322,17 @@ static void ide_error_cmd(ide_drive_t *d
void ide_finish_cmd(ide_drive_t *drive, struct ide_cmd *cmd, u8 stat)
{
struct request *rq = drive->hwif->rq;
- u8 err = ide_read_error(drive);
+ u8 err = ide_read_error(drive), nsect = cmd->tf.nsect;
+ u8 set_xfer = !!(cmd->tf_flags & IDE_TFLAG_SET_XFER);

ide_complete_cmd(drive, cmd, stat, err);
rq->errors = err;
+
+ if (err == 0 && set_xfer) {
+ ide_set_xfer_rate(drive, nsect);
+ ide_driveid_update(drive);
+ }
+
ide_complete_rq(drive, err ? -EIO : 0, blk_rq_bytes(rq));
}

Index: b/include/linux/ide.h
===================================================================
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -258,6 +258,7 @@ enum {
IDE_TFLAG_DYN = (1 << 5),
IDE_TFLAG_FS = (1 << 6),
IDE_TFLAG_MULTI_PIO = (1 << 7),
+ IDE_TFLAG_SET_XFER = (1 << 8),
};

enum {
@@ -294,7 +295,7 @@ struct ide_cmd {
} out, in;
} valid;

- u8 tf_flags;
+ u16 tf_flags;
u8 ftf_flags; /* for TASKFILE ioctl */
int protocol;


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