fix proc_fill_cache() in case of d_alloc_parallel() failure

If d_alloc_parallel() returns ERR_PTR(...), we don't want to dput()
that.  Small reorganization allows to have all error-in-lookup
cases rejoin the main codepath after dput(child), avoiding the
entire problem.

Spotted-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Fixes: 0168b9e38c42 "procfs: switch instantiate_t to d_splice_alias()"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index de22c2002b38..6f927340db0a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1891,19 +1891,19 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx,
                         struct dentry *res;
                         res = instantiate(child, task, ptr);
                         d_lookup_done(child);
-                        if (IS_ERR(res))
-                                goto end_instantiate;
                         if (unlikely(res)) {
                                 dput(child);
                                 child = res;
+                                if (IS_ERR(child))
+                                        goto end_instantiate;
                         }
                 }
         }
         inode = d_inode(child);
         ino = inode->i_ino;
         type = inode->i_mode >> 12;
-end_instantiate:
         dput(child);
+end_instantiate:
         return dir_emit(ctx, name, len, ino, type);
 }