Patch "ubifs: skip dumping tnc tree when zroot is null" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    ubifs: skip dumping tnc tree when zroot is null

to the 6.1-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:
     ubifs-skip-dumping-tnc-tree-when-zroot-is-null.patch
and it can be found in the queue-6.1 subdirectory.

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



commit c27611e70f8f3f0e8d625ac8cddc9f3c5f2bd495
Author: pangliyuan <pangliyuan1@xxxxxxxxxx>
Date:   Tue Dec 24 16:18:23 2024 +0800

    ubifs: skip dumping tnc tree when zroot is null
    
    [ Upstream commit bdb0ca39e0acccf6771db49c3f94ed787d05f2d7 ]
    
    Clearing slab cache will free all znode in memory and make
    c->zroot.znode = NULL, then dumping tnc tree will access
    c->zroot.znode which cause null pointer dereference.
    
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=219624#c0
    Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
    Signed-off-by: pangliyuan <pangliyuan1@xxxxxxxxxx>
    Reviewed-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
    Signed-off-by: Richard Weinberger <richard@xxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 3f128b9fdfbb2..9613725ed1935 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -946,16 +946,20 @@ void ubifs_dump_tnc(struct ubifs_info *c)
 
 	pr_err("\n");
 	pr_err("(pid %d) start dumping TNC tree\n", current->pid);
-	znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, NULL);
-	level = znode->level;
-	pr_err("== Level %d ==\n", level);
-	while (znode) {
-		if (level != znode->level) {
-			level = znode->level;
-			pr_err("== Level %d ==\n", level);
+	if (c->zroot.znode) {
+		znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, NULL);
+		level = znode->level;
+		pr_err("== Level %d ==\n", level);
+		while (znode) {
+			if (level != znode->level) {
+				level = znode->level;
+				pr_err("== Level %d ==\n", level);
+			}
+			ubifs_dump_znode(c, znode);
+			znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, znode);
 		}
-		ubifs_dump_znode(c, znode);
-		znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, znode);
+	} else {
+		pr_err("empty TNC tree in memory\n");
 	}
 	pr_err("(pid %d) finish dumping TNC tree\n", current->pid);
 }