5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: NeilBrown <neilb@xxxxxxx>
[ Upstream commit 88956eabfdea7d01d550535af120d4ef265b1d02 ]
If /proc/fs/nfsd/pool_stats is open when the last nfsd thread exits, then
when the file is closed a NULL pointer is dereferenced.
This is because nfsd_pool_stats_release() assumes that the
pointer to the svc_serv cannot become NULL while a reference is held.
This used to be the case but a recent patch split nfsd_last_thread() out
from nfsd_put(), and clearing the pointer is done in nfsd_last_thread().
This is easily reproduced by running
rpc.nfsd 8 ; ( rpc.nfsd 0;true) < /proc/fs/nfsd/pool_stats
Fortunately nfsd_pool_stats_release() has easy access to the svc_serv
pointer, and so can call svc_put() on it directly.
Fixes: 9f28a971ee9f ("nfsd: separate nfsd_last_thread() from nfsd_put()")
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/nfsd/nfssvc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index ee5713fca1870..2a1dd580dfb94 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -1084,11 +1084,12 @@ int nfsd_pool_stats_open(struct inode *inode, struct file *file)
int nfsd_pool_stats_release(struct inode *inode, struct file *file)
{
+ struct seq_file *seq = file->private_data;
+ struct svc_serv *serv = seq->private;
int ret = seq_release(inode, file);
- struct net *net = inode->i_sb->s_fs_info;
mutex_lock(&nfsd_mutex);
- nfsd_put(net);
+ svc_put(serv);
mutex_unlock(&nfsd_mutex);
return ret;
}
--
2.43.0
