Patch "hostfs: fix string handling in __dentry_name()" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    hostfs: fix string handling in __dentry_name()

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hostfs-fix-string-handling-in-__dentry_name.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1e18f15bf61275644d405ffd49688ee561f6b8ac
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date:   Sat Jan 11 01:37:44 2025 -0500

    hostfs: fix string handling in __dentry_name()
    
    [ Upstream commit 60a6002432448bb3f291d80768ae98d62efc9c77 ]
    
    strcpy() should not be used with destination potentially overlapping
    the source; what's more, strscpy() in there is pointless - we already
    know the amount we want to copy; might as well use memcpy().
    
    Fixes: c278e81b8a02 "hostfs: Remove open coded strcpy()"
    Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 1fb8eacb9817f..1efbcfa1f1f88 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -93,32 +93,17 @@ __uml_setup("hostfs=", hostfs_args,
 static char *__dentry_name(struct dentry *dentry, char *name)
 {
 	char *p = dentry_path_raw(dentry, name, PATH_MAX);
-	char *root;
-	size_t len;
-	struct hostfs_fs_info *fsi;
-
-	fsi = dentry->d_sb->s_fs_info;
-	root = fsi->host_root_path;
-	len = strlen(root);
-	if (IS_ERR(p)) {
-		__putname(name);
-		return NULL;
-	}
-
-	/*
-	 * This function relies on the fact that dentry_path_raw() will place
-	 * the path name at the end of the provided buffer.
-	 */
-	BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
+	struct hostfs_fs_info *fsi = dentry->d_sb->s_fs_info;
+	char *root = fsi->host_root_path;
+	size_t len = strlen(root);
 
-	strscpy(name, root, PATH_MAX);
-	if (len > p - name) {
+	if (IS_ERR(p) || len > p - name) {
 		__putname(name);
 		return NULL;
 	}
 
-	if (p > name + len)
-		strcpy(name + len, p);
+	memcpy(name, root, len);
+	memmove(name + len, p, name + PATH_MAX - p);
 
 	return name;
 }