From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit d20cb71dbf3487f24549ede1a8e2d67579b4632e ]
In "NFSv4: Move dentry instantiation into the NFSv4-specific atomic open code"
unconditional d_drop() after the ->open_context() had been removed. It had
been correct for success cases (there ->open_context() itself had been doing
dcache manipulations), but not for error ones. Only one of those (ENOENT)
got a compensatory d_drop() added in that commit, but in fact it should've
been done for all errors. As it is, the case of O_CREAT non-exclusive open
on a hashed negative dentry racing with e.g. symlink creation from another
client ended up with ->open_context() getting an error and proceeding to
call nfs_lookup(). On a hashed dentry, which would've instantly triggered
BUG_ON() in d_materialise_unique() (or, these days, its equivalent in
d_splice_alias()).
Cc: stable@xxxxxxxxxxxxxxx # v3.10+
Tested-by: Oleg Drokin <green@xxxxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
fs/nfs/dir.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 7a8d67c..29b7a75 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1529,9 +1529,9 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
err = PTR_ERR(inode);
trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
put_nfs_open_context(ctx);
+ d_drop(dentry);
switch (err) {
case -ENOENT:
- d_drop(dentry);
d_add(dentry, NULL);
nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
break;
--
2.5.0
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