[PATCH] nvmet: Don't overflow subsysnqn

[Leo Stone]

nvmet_root_discovery_nqn_store treats the subsysnqn string like a fixed
size buffer, even though it is dynamically allocated to the size of the
string.

Create a new string with kstrdup instead of using the old buffer.

Reported-by: syzbot+ff4aab278fa7e27e0f9e@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=ff4aab278fa7e27e0f9e
Fixes: 95409e277d83 ("nvmet: implement unique discovery NQN")
Signed-off-by: Leo Stone <leocstone@xxxxxxxxx>
---
 drivers/nvme/target/configfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index eeee9e9b854c..3fa25f9f7d92 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -2271,8 +2271,8 @@ static ssize_t nvmet_root_discovery_nqn_store(struct config_item *item,
 			return -EINVAL;
 		}
 	}
-	memset(nvmet_disc_subsys->subsysnqn, 0, NVMF_NQN_FIELD_LEN);
-	memcpy(nvmet_disc_subsys->subsysnqn, page, len);
+	kfree(nvmet_disc_subsys->subsysnqn);
+	nvmet_disc_subsys->subsysnqn = kstrdup(page, GFP_KERNEL);
 	up_write(&nvmet_config_sem);
 
 	return len;
-- 
2.43.0