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Subject[PATCH] oops in raw.c + fix
The next patch in the dev_t series eliminates the last applied use
of MAX_BLKDEV - only the definition in major.h remains.

Sneaky as I am, I combine this patch with the fix for an Oops:
On open, raw_open does
filp->f_dentry->d_inode->i_mapping =
bdev->bd_inode->i_mapping;
storing a pointer to bdev stuff.
But on release this pointer stayed, the block device is not
referenced anymore and disappears, and the next open references
undefined stuff.
I checked, and this can actually cause an Oops - scenario:
# raw /dev/raw/raw12 /dev/hdf
# dd if=/dev/raw/raw12 of=/dev/null bs=512 count=1
# raw /dev/raw/raw12 0 0
# dd if=/dev/raw/raw12 of=/dev/null bs=512 count=1
Oops.

More precisely the problem is that dentry_open does
file_ra_state_init(&f->f_ra, inode->i_mapping);
And file_ra_state_init uses mapping->backing_dev_info->ra_pages.
Ugly, to use so much information about the inode even before
the inode has been opened.

In the patch below I reset i_mapping upon release of the raw device.

Andries

---
diff -u --recursive --new-file -X /linux/dontdiff a/drivers/char/raw.c b/drivers/char/raw.c
--- a/drivers/char/raw.c Thu Jan 9 18:07:10 2003
+++ b/drivers/char/raw.c Sat Mar 8 15:24:14 2003
@@ -19,14 +19,16 @@

#include <asm/uaccess.h>

+#define MAX_RAW_MINORS 256
+
struct raw_device_data {
struct block_device *binding;
int inuse;
};

-static struct raw_device_data raw_devices[256];
+static struct raw_device_data raw_devices[MAX_RAW_MINORS];
static DECLARE_MUTEX(raw_mutex);
-static struct file_operations raw_ctl_fops;
+static struct file_operations raw_ctl_fops; /* forward dclaration */

/*
* Open/close code for raw IO.
@@ -85,11 +87,16 @@
{
const int minor= minor(inode->i_rdev);
struct block_device *bdev;
-
+
down(&raw_mutex);
bdev = raw_devices[minor].binding;
raw_devices[minor].inuse--;
up(&raw_mutex);
+
+ /* Here inode->i_mapping == bdev->bd_inode->i_mapping */
+ inode->i_mapping = &inode->i_data;
+ inode->i_mapping->backing_dev_info = &default_backing_dev_info;
+
bd_release(bdev);
blkdev_put(bdev, BDEV_RAW);
return 0;
@@ -130,11 +137,13 @@
goto out;

err = -EINVAL;
- if (rq.raw_minor < 0 || rq.raw_minor > MINORMASK)
+ if (rq.raw_minor < 0 || rq.raw_minor >= MAX_RAW_MINORS)
goto out;
rawdev = &raw_devices[rq.raw_minor];

if (command == RAW_SETBIND) {
+ dev_t dev;
+
/*
* This is like making block devices, so demand the
* same capability
@@ -151,9 +160,10 @@
*/

err = -EINVAL;
+ dev = MKDEV(rq.block_major, rq.block_minor);
if ((rq.block_major == 0 && rq.block_minor != 0) ||
- rq.block_major > MAX_BLKDEV ||
- rq.block_minor > MINORMASK)
+ MAJOR(dev) != rq.block_major ||
+ MINOR(dev) != rq.block_minor)
goto out;

down(&raw_mutex);
@@ -170,10 +180,7 @@
/* unbind */
rawdev->binding = NULL;
} else {
- kdev_t kdev;
-
- kdev = mk_kdev(rq.block_major, rq.block_minor);
- rawdev->binding = bdget(kdev_t_to_nr(kdev));
+ rawdev->binding = bdget(dev);
MOD_INC_USE_COUNT;
}
up(&raw_mutex);
-
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