[PATCH] dm: fix mapped device ref counting

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>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 8edd643..f7e7436 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -102,8 +102,10 @@ static struct hash_cell *__get_name_cell(const char *str)
        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(const char *str)
        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 hash_cell *hc)
  */
 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 *name, const char *uuid, struct mapped_devi
         * 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 *old, const char *new)
        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 *old, const char *new)
                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_hash_cell(struct dm_ioctl *param)
                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(struct dm_ioctl *param)
        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(struct dm_ioctl *param)
 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 *param, size_t param_size)
                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 *param)
        }
 
        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 *param, size_t param_size)
 {
        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, size_t param_size)
        param->flags &= ~DM_INACTIVE_PRESENT_FLAG;
 
        r = __dev_status(hc->md, param);
+       md = hc->md;
        up_write(&_hash_lock);
+       dm_put(md);
        return r;
 }