[PATCH] f2fs: fix potential use-after-free issue

[Chao Yu]

In error path of f2fs_read_multi_pages(), it should let last referrer
release decompress io context memory, otherwise, other referrer will
cause use-after-free issue.

Fixes: 4c8ff7095bef ("f2fs: support data compression")
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 fs/f2fs/data.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 4adf28bdd022..48a622b95b76 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2208,16 +2208,16 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 					page->index, for_write);
 			if (IS_ERR(bio)) {
 				ret = PTR_ERR(bio);
-				bio = NULL;
 				dic->failed = true;
 				if (refcount_sub_and_test(dic->nr_cpages - i,
-							&dic->ref))
+							&dic->ref)) {
 					f2fs_decompress_end_io(dic->rpages,
 							cc->cluster_size, true,
 							false);
-				f2fs_free_dic(dic);
+					f2fs_free_dic(dic);
+				}
 				f2fs_put_dnode(&dn);
-				*bio_ret = bio;
+				*bio_ret = NULL;
 				return ret;
 			}
 		}
-- 
2.18.0.rc1