[PATCH V2] lightnvm: protect target type list with correct locks

[Rakesh Pandit]

nvm_tgt_types list was protected by wrong lock for NVM_INFO ioctl call
and can race with addition or removal of target types.  Also
unregistering target type was not protected correctly.

Fixes: 5cd907853 ("lightnvm: remove nested lock conflict with mm")
Signed-off-by: Rakesh Pandit <rak...@tuxera.com>
---

V2: also add correct lock while unregistering and fix "Fixes" tag at
end.  Note I found these while investigating another issue and
skimming the core code but worth fixing.

 drivers/lightnvm/core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index 9f9a137..1b8338d 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -589,9 +589,9 @@ void nvm_unregister_tgt_type(struct nvm_tgt_type *tt)
        if (!tt)
                return;
 
-       down_write(&nvm_lock);
+       down_write(&nvm_tgtt_lock);
        list_del(&tt->list);
-       up_write(&nvm_lock);
+       up_write(&nvm_tgtt_lock);
 }
 EXPORT_SYMBOL(nvm_unregister_tgt_type);
 
@@ -1190,7 +1190,7 @@ static long nvm_ioctl_info(struct file *file, void __user 
*arg)
        info->version[1] = NVM_VERSION_MINOR;
        info->version[2] = NVM_VERSION_PATCH;
 
-       down_write(&nvm_lock);
+       down_write(&nvm_tgtt_lock);
        list_for_each_entry(tt, &nvm_tgt_types, list) {
                struct nvm_ioctl_info_tgt *tgt = &info->tgts[tgt_iter];
 
@@ -1203,7 +1203,7 @@ static long nvm_ioctl_info(struct file *file, void __user 
*arg)
        }
 
        info->tgtsize = tgt_iter;
-       up_write(&nvm_lock);
+       up_write(&nvm_tgtt_lock);
 
        if (copy_to_user(arg, info, sizeof(struct nvm_ioctl_info))) {
                kfree(info);
-- 
2.7.4