From: Jeff Mahoney Date: Mon, 26 Jun 2006 07:27:24 +0000 (-0700) Subject: [PATCH] dm: fix mapped device ref counting X-Git-Tag: v2.6.18-rc1~664 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7ec75f254742766eb729f1d1024a5b4e6692fc5f;p=linux-2.6 [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 Signed-off-by: Alasdair G Kergon Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 8edd643541..f7e743691a 100644 --- 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; }