main - toolcontext: fix double free (core dumped) issue

[David Teigland <teigland@sourceware.org>]

Gitweb:        https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=db22a389cfb12eef77dfc2e1ce124ac83ed6c5a2
Commit:        db22a389cfb12eef77dfc2e1ce124ac83ed6c5a2
Parent:        66daedc6d27d07e4bcd43ee0286e21a69fdc33d9
Author:        Heming Zhao <heming.zhao@suse.com>
AuthorDate:    Tue Jul 13 03:01:00 2021 +0800
Committer:     David Teigland <teigland@redhat.com>
CommitterDate: Mon Jul 12 14:10:21 2021 -0500

toolcontext: fix double free (core dumped) issue

How to trigger:

```
~ # export LVM_SYSTEM_DIR=_
~ # pvscan
  No matching physical volumes found
double free or corruption (!prev)
Aborted (core dumped)
```

when LVM_SYSTEM_DIR is empty, _load_config_file() won't be called.

when LVM_SYSTEM_DIR is not empty, cfl->cft links into cmd->config_files
by _load_config_file()@lib/commands/toolcontext.c

core dumped code: _destroy_config()@lib/commands/toolcontext.c

```
    /* CONFIG_FILE/CONFIG_MERGED_FILES */
    if ((cft = remove_config_tree_by_source(cmd, CONFIG_MERGED_FILES)))
        config_destroy(cft);
    else if ((cft = remove_config_tree_by_source(cmd, CONFIG_FILE)))
        config_destroy(cft); <=== first free the cft

    dm_list_iterate_items(cfl, &cmd->config_files)
        config_destroy(cfl->cft); <=== double free the cft
```

Fixes: c43f2f8ae08ed0555a300764c8644ea56f4f41e2

Signed-off-by: Heming Zhao <heming.zhao@suse.com>
---
 lib/commands/toolcontext.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c
index b295a20ef..742bdd9c2 100644
--- a/lib/commands/toolcontext.c
+++ b/lib/commands/toolcontext.c
@@ -966,8 +966,13 @@ static void _destroy_config(struct cmd_context *cmd)
 	/* CONFIG_FILE/CONFIG_MERGED_FILES */
 	if ((cft = remove_config_tree_by_source(cmd, CONFIG_MERGED_FILES)))
 		config_destroy(cft);
-	else if ((cft = remove_config_tree_by_source(cmd, CONFIG_FILE)))
+	else if ((cft = remove_config_tree_by_source(cmd, CONFIG_FILE))) {
+		dm_list_iterate_items(cfl, &cmd->config_files) {
+			if (cfl->cft == cft)
+				dm_list_del(&cfl->list);
+		}
 		config_destroy(cft);
+	}
 
 	dm_list_iterate_items(cfl, &cmd->config_files)
 		config_destroy(cfl->cft);