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Subject[patch 13/37] dm: fix mapped device ref counting
-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Jeff Mahoney <jeffm@suse.com>

To avoid races, _minor_lock must be held while changing mapped device
reference counts.

There are a few paths where a mapped_device pointer is returned before a
reference is taken. This patch fixes them.

[akpm: too late for 2.6.17 - suitable for 2.6.17.x after it has settled]

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/md/dm-ioctl.c | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
--- linux-2.6.17.11.orig/drivers/md/dm-ioctl.c
+++ linux-2.6.17.11/drivers/md/dm-ioctl.c
@@ -102,8 +102,10 @@ static struct hash_cell *__get_name_cell
unsigned int h = hash_str(str);

list_for_each_entry (hc, _name_buckets + h, name_list)
- if (!strcmp(hc->name, str))
+ if (!strcmp(hc->name, str)) {
+ dm_get(hc->md);
return hc;
+ }

return NULL;
}
@@ -114,8 +116,10 @@ static struct hash_cell *__get_uuid_cell
unsigned int h = hash_str(str);

list_for_each_entry (hc, _uuid_buckets + h, uuid_list)
- if (!strcmp(hc->uuid, str))
+ if (!strcmp(hc->uuid, str)) {
+ dm_get(hc->md);
return hc;
+ }

return NULL;
}
@@ -191,7 +195,7 @@ static int unregister_with_devfs(struct
*/
static int dm_hash_insert(const char *name, const char *uuid, struct mapped_device *md)
{
- struct hash_cell *cell;
+ struct hash_cell *cell, *hc;

/*
* Allocate the new cells.
@@ -204,14 +208,19 @@ static int dm_hash_insert(const char *na
* Insert the cell into both hash tables.
*/
down_write(&_hash_lock);
- if (__get_name_cell(name))
+ hc = __get_name_cell(name);
+ if (hc) {
+ dm_put(hc->md);
goto bad;
+ }

list_add(&cell->name_list, _name_buckets + hash_str(name));

if (uuid) {
- if (__get_uuid_cell(uuid)) {
+ hc = __get_uuid_cell(uuid);
+ if (hc) {
list_del(&cell->name_list);
+ dm_put(hc->md);
goto bad;
}
list_add(&cell->uuid_list, _uuid_buckets + hash_str(uuid));
@@ -289,6 +298,7 @@ static int dm_hash_rename(const char *ol
if (hc) {
DMWARN("asked to rename to an already existing name %s -> %s",
old, new);
+ dm_put(hc->md);
up_write(&_hash_lock);
kfree(new_name);
return -EBUSY;
@@ -328,6 +338,7 @@ static int dm_hash_rename(const char *ol
dm_table_put(table);
}

+ dm_put(hc->md);
up_write(&_hash_lock);
kfree(old_name);
return 0;
@@ -611,10 +622,8 @@ static struct hash_cell *__find_device_h
return __get_name_cell(param->name);

md = dm_get_md(huge_decode_dev(param->dev));
- if (md) {
+ if (md)
mdptr = dm_get_mdptr(md);
- dm_put(md);
- }

return mdptr;
}
@@ -628,7 +637,6 @@ static struct mapped_device *find_device
hc = __find_device_hash_cell(param);
if (hc) {
md = hc->md;
- dm_get(md);

/*
* Sneakily write in both the name and the uuid
@@ -653,6 +661,7 @@ static struct mapped_device *find_device
static int dev_remove(struct dm_ioctl *param, size_t param_size)
{
struct hash_cell *hc;
+ struct mapped_device *md;

down_write(&_hash_lock);
hc = __find_device_hash_cell(param);
@@ -663,8 +672,11 @@ static int dev_remove(struct dm_ioctl *p
return -ENXIO;
}

+ md = hc->md;
+
__hash_remove(hc);
up_write(&_hash_lock);
+ dm_put(md);
param->data_size = 0;
return 0;
}
@@ -790,7 +802,6 @@ static int do_resume(struct dm_ioctl *pa
}

md = hc->md;
- dm_get(md);

new_map = hc->new_map;
hc->new_map = NULL;
@@ -1078,6 +1089,7 @@ static int table_clear(struct dm_ioctl *
{
int r;
struct hash_cell *hc;
+ struct mapped_device *md;

down_write(&_hash_lock);

@@ -1096,7 +1108,9 @@ static int table_clear(struct dm_ioctl *
param->flags &= ~DM_INACTIVE_PRESENT_FLAG;

r = __dev_status(hc->md, param);
+ md = hc->md;
up_write(&_hash_lock);
+ dm_put(md);
return r;
}

--
-
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