Merge: CVE-2024-49967: ext4: no need to continue when the number of entries is 1

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5599

JIRA: https://issues.redhat.com/browse/RHEL-64524  
CVE: CVE-2024-49967

```
ext4: no need to continue when the number of entries is 1

Fixes: ac27a0e ("[PATCH] ext4: initial copy of files from ext3")
Reported-by: syzbot+ae688d469e36fb5138d0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: syzbot+ae688d469e36fb5138d0@syzkaller.appspotmail.com
Link: https://patch.msgid.link/tencent_BE7AEE6C7C2D216CB8949CE8E6EE7ECC2C0A@qq.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
(cherry picked from commit 1a00a39)
```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

---

<small>Created 2024-10-28 14:56 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://gitlab.com/cki-project/kernel-workflow/-/issues/new?issue%5Btitle%5D=backporter%20webhook%20issue)</small>

Approved-by: Brian Foster <bfoster@redhat.com>
Approved-by: Chris von Recklinghausen <crecklin@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

fs/ext4/namei.c

@@ -2046,7 +2046,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
 		split = count/2;
 
 	hash2 = map[split].hash;
-	continued = hash2 == map[split - 1].hash;
+	continued = split > 0 ? hash2 == map[split - 1].hash : 0;
 	dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",
 			(unsigned long)dx_get_block(frame->at),
 					hash2, split, count-split));