linux-kernel - Re: [syzbot] [mm?] possible deadlock in lock_next

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250715012717.4112-1-hdanton@sina.com>
Date: Tue, 15 Jul 2025 09:27:16 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+159a3ef1894076a6a6e9@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] possible deadlock in lock_next_vma

> Date: Mon, 14 Jul 2025 09:38:33 -0700	[thread overview]
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    0be23810e32e Add linux-next specific files for 20250714
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15cfb0f0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=be9e2082003f81ff
> dashboard link: https://syzkaller.appspot.com/bug?extid=159a3ef1894076a6a6e9
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1003b18c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11437d82580000

#syz test

--- x/fs/proc/task_mmu.c
+++ y/fs/proc/task_mmu.c
@@ -585,6 +585,7 @@ no_vma:
 	return ERR_PTR(-ENOENT);
 }
 
+static DEFINE_MUTEX(query_mutex);
 static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
 {
 	struct procmap_query karg;
@@ -620,8 +621,10 @@ static int do_procmap_query(struct proc_
 	if (!mm || !mmget_not_zero(mm))
 		return -ESRCH;
 
+	mutex_lock(&query_mutex);
 	err = query_vma_setup(priv);
 	if (err) {
+		mutex_unlock(&query_mutex);
 		mmput(mm);
 		return err;
 	}
@@ -712,6 +715,7 @@ static int do_procmap_query(struct proc_
 
 	/* unlock vma or mmap_lock, and put mm_struct before copying data to user */
 	query_vma_teardown(priv);
+	mutex_unlock(&query_mutex);
 	mmput(mm);
 
 	if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr),
@@ -732,6 +736,7 @@ static int do_procmap_query(struct proc_
 
 out:
 	query_vma_teardown(priv);
+	mutex_unlock(&query_mutex);
 	mmput(mm);
 	kfree(name_buf);
 	return err;
--