| Message ID | 169448190063.19905.9707641304438290692@noble.neil.brown.name (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | NFSD: fix possible oops when nfsd/pool_stats is closed. | expand |
On Tue, Sep 12, 2023 at 11:25:00AM +1000, NeilBrown wrote: > > 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@suse.de> > --- > fs/nfsd/nfssvc.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) Thanks, applied to nfsd-fixes (for v6.6-rc). > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c > index 1582af33e204..551c16a72012 100644 > --- a/fs/nfsd/nfssvc.c > +++ b/fs/nfsd/nfssvc.c > @@ -1082,11 +1082,12 @@ int nfsd_pool_stats_open(struct inode *inode, struct file *file) > > int nfsd_pool_stats_release(struct inode *inode, struct file *file) > { > + struct svc_serv *serv = > + ((struct seq_file *) file->private_data)->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; > } > -- > 2.42.0 >
On Tue, 2023-09-12 at 11:25 +1000, NeilBrown wrote: > 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@suse.de> > --- > 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 1582af33e204..551c16a72012 100644 > --- a/fs/nfsd/nfssvc.c > +++ b/fs/nfsd/nfssvc.c > @@ -1082,11 +1082,12 @@ int nfsd_pool_stats_open(struct inode *inode, struct file *file) > > int nfsd_pool_stats_release(struct inode *inode, struct file *file) > { > + struct svc_serv *serv = > + ((struct seq_file *) file->private_data)->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; > } Reviewed-by: Jeff Layton <jlayton@kernel.org>
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index 1582af33e204..551c16a72012 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -1082,11 +1082,12 @@ int nfsd_pool_stats_open(struct inode *inode, struct file *file) int nfsd_pool_stats_release(struct inode *inode, struct file *file) { + struct svc_serv *serv = + ((struct seq_file *) file->private_data)->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; }
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@suse.de> --- fs/nfsd/nfssvc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)