From: Hongbo Li <lihongbo22@huawei.com>
Date: Sat, 11 Oct 2025 09:22:35 +0000 (+0000)
Subject: hostfs: Fix only passing host root in boot stage with new mount
X-Git-Tag: v6.17.9~122
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a57b84bc82fbc6e31293fb6a770a86294d769e8;p=thirdparty%2Fkernel%2Fstable.git

hostfs: Fix only passing host root in boot stage with new mount

[ Upstream commit 2c2b67af5f5f77fc68261a137ad65dcfb8e52506 ]

In the old mount proceedure, hostfs could only pass root directory during
boot. This is because it constructed the root directory using the @root_ino
event without any mount options. However, when using it with the new mount
API, this step is no longer triggered. As a result, if users mounts without
specifying any mount options, the @host_root_path remains uninitialized. To
prevent this issue, the @host_root_path should be initialized at the time
of allocation.

Reported-by: Geoffrey Thorpe <geoff@geoffthorpe.net>
Closes: https://lore.kernel.org/all/643333a0-f434-42fb-82ac-d25a0b56f3b7@geoffthorpe.net/
Fixes: cd140ce9f611 ("hostfs: convert hostfs to use the new mount API")
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Link: https://patch.msgid.link/20251011092235.29880-1-lihongbo22@huawei.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 01e516175bcd7..30fcce80a2c35 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -979,7 +979,7 @@ static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct hostfs_fs_info *fsi = fc->s_fs_info;
 	struct fs_parse_result result;
-	char *host_root;
+	char *host_root, *tmp_root;
 	int opt;
 
 	opt = fs_parse(fc, hostfs_param_specs, param, &result);
@@ -990,11 +990,13 @@ static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_hostfs:
 		host_root = param->string;
 		if (!*host_root)
-			host_root = "";
-		fsi->host_root_path =
-			kasprintf(GFP_KERNEL, "%s/%s", root_ino, host_root);
-		if (fsi->host_root_path == NULL)
+			break;
+		tmp_root = kasprintf(GFP_KERNEL, "%s%s",
+				     fsi->host_root_path, host_root);
+		if (!tmp_root)
 			return -ENOMEM;
+		kfree(fsi->host_root_path);
+		fsi->host_root_path = tmp_root;
 		break;
 	}
 
@@ -1004,17 +1006,17 @@ static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 static int hostfs_parse_monolithic(struct fs_context *fc, void *data)
 {
 	struct hostfs_fs_info *fsi = fc->s_fs_info;
-	char *host_root = (char *)data;
+	char *tmp_root, *host_root = (char *)data;
 
 	/* NULL is printed as '(null)' by printf(): avoid that. */
 	if (host_root == NULL)
-		host_root = "";
+		return 0;
 
-	fsi->host_root_path =
-		kasprintf(GFP_KERNEL, "%s/%s", root_ino, host_root);
-	if (fsi->host_root_path == NULL)
+	tmp_root = kasprintf(GFP_KERNEL, "%s%s", fsi->host_root_path, host_root);
+	if (!tmp_root)
 		return -ENOMEM;
-
+	kfree(fsi->host_root_path);
+	fsi->host_root_path = tmp_root;
 	return 0;
 }
 
@@ -1049,6 +1051,11 @@ static int hostfs_init_fs_context(struct fs_context *fc)
 	if (!fsi)
 		return -ENOMEM;
 
+	fsi->host_root_path = kasprintf(GFP_KERNEL, "%s/", root_ino);
+	if (!fsi->host_root_path) {
+		kfree(fsi);
+		return -ENOMEM;
+	}
 	fc->s_fs_info = fsi;
 	fc->ops = &hostfs_context_ops;
 	return 0;