[PATCH] ntfs: Fix null pointer dereference

[Ethan Tidmore <ethantidmore06@gmail.com>]

The variable ctx can be null and once confirmed to be null in its error
path goes to label err_out. Once there it can be immediately dereferenced
by the function ntfs_attr_put_search_ctx() which has no null pointer check.

Detected by Smatch:
fs/ntfs/ea.c:687 ntfs_new_attr_flags() error: 
we previously assumed 'ctx' could be null (see line 577)

Add null pointer check before running  ntfs_attr_put_search_ctx() in 
error path.

Fixes: fc053f05ca282 ("ntfs: add reparse and ea operations")
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
---
 fs/ntfs/ea.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs/ea.c b/fs/ntfs/ea.c
index 82ad9b61ec64..b2b0a9a043a9 100644
--- a/fs/ntfs/ea.c
+++ b/fs/ntfs/ea.c
@@ -684,7 +684,8 @@ static int ntfs_new_attr_flags(struct ntfs_inode *ni, __le32 fattr)
 	a->flags = new_aflags;
 	mark_mft_record_dirty(ctx->ntfs_ino);
 err_out:
-	ntfs_attr_put_search_ctx(ctx);
+	if (ctx)
+		ntfs_attr_put_search_ctx(ctx);
 	unmap_mft_record(ni);
 	return err;
 }
-- 
2.53.0