[PATCH v1] erofs: Fix state inconsistency when updating fsid/domain_id

[Baolin Liu]

From: Baolin Liu <liubaolin at kylinos.cn>

When updating fsid or domain_id, the code frees the old pointer before
allocating a new one. If allocation fails, the pointer becomes NULL
while the old value is already freed, causing state inconsistency.

Fix by allocating the new value first, and only freeing the old value
on success.

Signed-off-by: Baolin Liu <liubaolin at kylinos.cn>
---
 fs/erofs/super.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 937a215f626c..6e083d7e634c 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -509,16 +509,22 @@ static int erofs_fc_parse_param(struct fs_context *fc,
 		break;
 #ifdef CONFIG_EROFS_FS_ONDEMAND
 	case Opt_fsid:
-		kfree(sbi->fsid);
-		sbi->fsid = kstrdup(param->string, GFP_KERNEL);
-		if (!sbi->fsid)
+		char *new_fsid;
+
+		new_fsid = kstrdup(param->string, GFP_KERNEL);
+		if (!new_fsid)
 			return -ENOMEM;
+		kfree(sbi->fsid);
+		sbi->fsid = new_fsid;
 		break;
 	case Opt_domain_id:
-		kfree(sbi->domain_id);
-		sbi->domain_id = kstrdup(param->string, GFP_KERNEL);
-		if (!sbi->domain_id)
+		char *new_domain_id;
+
+		new_domain_id = kstrdup(param->string, GFP_KERNEL);
+		if (!new_domain_id)
 			return -ENOMEM;
+		kfree(sbi->domain_id);
+		sbi->domain_id = new_domain_id;
 		break;
 #else
 	case Opt_fsid:
-- 
2.39.2