[PATCH AUTOSEL 6.6 12/40] nbd: factor out a helper to get nbd_config without holding 'config_lock'

Sasha Levin
2023-11-28T21:07:19Z

From: Li Nan <linan122@huawei.com>

[ Upstream commit 3123ac77923341774ca3ad1196ad20bb0732bf70 ]

There are no functional changes, just to make code cleaner and prepare
to fix null-ptr-dereference while accessing 'nbd->config'.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20231116162316.1740402-3-linan666@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/nbd.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 02f844832d912..daaf8805e876c 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -395,6 +395,14 @@ static u32 req_to_nbd_cmd_type(struct request *req)
}
}

+static struct nbd_config *nbd_get_config_unlocked(struct nbd_device *nbd)
+{
+ if (refcount_inc_not_zero(&nbd->config_refs))
+ return nbd->config;
+
+ return NULL;
+}
+
static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
{
struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
@@ -409,13 +417,13 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
return BLK_EH_DONE;
}

- if (!refcount_inc_not_zero(&nbd->config_refs)) {
+ config = nbd_get_config_unlocked(nbd);
+ if (!config) {
cmd->status = BLK_STS_TIMEOUT;
__clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
mutex_unlock(&cmd->lock);
goto done;
}
- config = nbd->config;

if (config->num_connections > 1 ||
(config->num_connections == 1 && nbd->tag_set.timeout)) {
@@ -977,12 +985,12 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
struct nbd_sock *nsock;
int ret;

- if (!refcount_inc_not_zero(&nbd->config_refs)) {
+ config = nbd_get_config_unlocked(nbd);
+ if (!config) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Socks array is empty\n");
return -EINVAL;
}
- config = nbd->config;

if (index >= config->num_connections) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
@@ -1560,6 +1568,7 @@ static int nbd_alloc_and_init_config(struct nbd_device *nbd)
static int nbd_open(struct gendisk *disk, blk_mode_t mode)
{
struct nbd_device *nbd;
+ struct nbd_config *config;
int ret = 0;

mutex_lock(&nbd_index_mutex);
@@ -1572,7 +1581,9 @@ static int nbd_open(struct gendisk *disk, blk_mode_t mode)
ret = -ENXIO;
goto out;
}
- if (!refcount_inc_not_zero(&nbd->config_refs)) {
+
+ config = nbd_get_config_unlocked(nbd);
+ if (!config) {
mutex_lock(&nbd->config_lock);
if (refcount_inc_not_zero(&nbd->config_refs)) {
mutex_unlock(&nbd->config_lock);
@@ -1588,7 +1599,7 @@ static int nbd_open(struct gendisk *disk, blk_mode_t mode)
mutex_unlock(&nbd->config_lock);
if (max_part)
set_bit(GD_NEED_PART_SCAN, &disk->state);
- } else if (nbd_disconnected(nbd->config)) {
+ } else if (nbd_disconnected(config)) {
if (max_part)
set_bit(GD_NEED_PART_SCAN, &disk->state);
}
@@ -2205,7 +2216,8 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
}
mutex_unlock(&nbd_index_mutex);

- if (!refcount_inc_not_zero(&nbd->config_refs)) {
+ config = nbd_get_config_unlocked(nbd);
+ if (!config) {
dev_err(nbd_to_dev(nbd),
"not configured, cannot reconfigure\n");
nbd_put(nbd);
@@ -2213,7 +2225,6 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
}

mutex_lock(&nbd->config_lock);
- config = nbd->config;
if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) ||
!nbd->pid) {
dev_err(nbd_to_dev(nbd),
--
2.42.0