Re: [PATCH] nfsd: fix dentry leak upon mkdir failure.

[bfields@xxxxxxxxxxxx (J. Bruce Fields)]

On Mon, Aug 12, 2019 at 11:16:11AM +0900, Tetsuo Handa wrote:
> syzbot is reporting that nfsd_mkdir() forgot to remove dentry created by
> d_alloc_name() when __nfsd_mkdir() failed (due to memory allocation fault
> injection) [1].

Thanks!  But it might be clearer to do this in the caller, in the same
place the dentry was allocated?

--b.

commit d6846bfbeeac
Author: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date:   Mon Aug 12 11:16:11 2019 +0900

    nfsd: fix dentry leak upon mkdir failure.
    
    syzbot is reporting that nfsd_mkdir() forgot to remove dentry created by
    d_alloc_name() when __nfsd_mkdir() failed (due to memory allocation fault
    injection) [1].
    
    [1] https://syzkaller.appspot.com/bug?id=ce41a1f769ea4637ebffedf004a803e8405b4674
    
    Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
    Reported-by: syzbot <syzbot+2c95195d5d433f6ed6cb@xxxxxxxxxxxxxxxxxxxxxxxxx>
    Fixes: e8a79fb14f6b76b5 ("nfsd: add nfsd/clients directory")
    [bfields: clean up in nfsd_mkdir instead of __nfsd_mkdir]
    Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 13c548733860..928a0b2c05dc 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1205,6 +1205,7 @@ static struct dentry *nfsd_mkdir(struct dentry *parent, struct nfsdfs_client *nc
 	inode_unlock(dir);
 	return dentry;
 out_err:
+	dput(dentry);
 	dentry = ERR_PTR(ret);
 	goto out;
 }