[PATCH] f2fs: fix to avoid memory leak in f2fs_rename()

[Chao Yu <chao@kernel.org>]

syzbot reported a f2fs bug as below:

BUG: memory leak
unreferenced object 0xffff888127f70830 (size 16):
  comm "syz.0.23", pid 6144, jiffies 4294943712
  hex dump (first 16 bytes):
    3c af 57 72 5b e6 8f ad 6e 8e fd 33 42 39 03 ff  <.Wr[...n..3B9..
  backtrace (crc 925f8a80):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4520 [inline]
    slab_alloc_node mm/slub.c:4844 [inline]
    __do_kmalloc_node mm/slub.c:5237 [inline]
    __kmalloc_noprof+0x3bd/0x560 mm/slub.c:5250
    kmalloc_noprof include/linux/slab.h:954 [inline]
    fscrypt_setup_filename+0x15e/0x3b0 fs/crypto/fname.c:364
    f2fs_setup_filename+0x52/0xb0 fs/f2fs/dir.c:143
    f2fs_rename+0x159/0xca0 fs/f2fs/namei.c:961
    f2fs_rename2+0xd5/0xf20 fs/f2fs/namei.c:1308
    vfs_rename+0x7ff/0x1250 fs/namei.c:6026
    filename_renameat2+0x4f4/0x660 fs/namei.c:6144
    __do_sys_renameat2 fs/namei.c:6173 [inline]
    __se_sys_renameat2 fs/namei.c:6168 [inline]
    __x64_sys_renameat2+0x59/0x80 fs/namei.c:6168
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is in commit 40b2d55e0452 ("f2fs: fix to create selinux
label during whiteout initialization"), we added a call to
f2fs_setup_filename() without a matching call to f2fs_free_filename(),
fix it.

Fixes: 40b2d55e0452 ("f2fs: fix to create selinux label during whiteout initialization")
Cc: stable@kernel.org
Reported-by: syzbot+cf7946ab25b21abc4b66@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/69a75fe1.a70a0220.b118c.0014.GAE@google.com
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/namei.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index e360f08a9586..6ef21deeef1c 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -964,6 +964,7 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 			return err;
 
 		err = f2fs_create_whiteout(idmap, old_dir, &whiteout, &fname);
+		f2fs_free_filename(&fname);
 		if (err)
 			return err;
 	}
-- 
2.49.0