btrfs-progs: Avoid double-free of fs_devices->list

I found the following patch is insufficient.

===============================================================================
commit 6e6b32ddf58db54f714d0f263c2589f4859e8b5e
Author: Adam Buchbinder <abuchbinder@google.com>
Date:   Fri Jun 13 16:43:56 2014 -0700

    btrfs-progs: Fix a use-after-free in the volumes code.
===============================================================================

"btrfs filesystem show <dev>" with this patch causes segmentation fault
if "<dev>" is a not-mounted Btrfs filesystem.

===============================================================================
Label: none  uuid: <cut here>
        Total devices 1 FS bytes used 112.00KiB
        devid    1 size 59.12GiB used 2.04GiB path /dev/sdd1

Segmentation fault (core dumped)
===============================================================================

It's due to double-free of fs_devices->list as follows.

===============================================================================
cmd_show
  -> list_del(&fs_devices->list)     # 1st one.
  -> btrfs_close_devices(fs_devices)
    -> list_del(&fs_devices->list)   # <- 2nd one introduced at 6e6b32dd.
                                          Double-free happens here.
===============================================================================

First list_del() can safely be removed because fs_devices->list will be
deleted by second one, soon.

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Adam Buchbinder <abuchbinder@google.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 888e3ec..6d7c13e 100644 (file)
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -656,7 +656,6 @@ devs_only:
        while (!list_empty(all_uuids)) {
                fs_devices = list_entry(all_uuids->next,
                                        struct btrfs_fs_devices, list);
-               list_del(&fs_devices->list);
                btrfs_close_devices(fs_devices);
        }
 out: