linux-kernel - [PATCH 5.15 1/1] ocfs2: fix deadlock in ocfs2_get_system_file

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>] [day] [month] [year] [list]

Message-ID: <20250522092838.2867777-1-d.privalov@omp.ru>
Date: Thu, 22 May 2025 12:28:37 +0300
From: Dmitriy Privalov <d.privalov@....ru>
To: <stable@...r.kernel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>, Joseph Qi
	<joseph.qi@...ux.alibaba.com>, <ocfs2-devel@....oracle.com>,
	<linux-kernel@...r.kernel.org>, <lvc-project@...uxtesting.org>, Mohammed
 Anees <pvmohammedanees2003@...il.com>,
	<syzbot+e0055ea09f1f5e6fabdd@...kaller.appspotmail.com>, Junxiao Bi
	<junxiao.bi@...cle.com>, Changwei Ge <gechangwei@...e.cn>, Gang He
	<ghe@...e.com>, Jun Piao <piaojun@...wei.com>, Andrew Morton
	<akpm@...ux-foundation.org>, Dmitriy Privalov <d.privalov@....ru>
Subject: [PATCH 5.15 1/1] ocfs2: fix deadlock in ocfs2_get_system_file_inode

From: Mohammed Anees <pvmohammedanees2003@...il.com>

commit 7bf1823e010e8db2fb649c790bd1b449a75f52d8 upstream.

syzbot has found a possible deadlock in ocfs2_get_system_file_inode [1].

The scenario is depicted here,

	CPU0					CPU1
lock(&ocfs2_file_ip_alloc_sem_key);
                               lock(&osb->system_file_mutex);
                               lock(&ocfs2_file_ip_alloc_sem_key);
lock(&osb->system_file_mutex);

The function calls which could lead to this are:

CPU0
ocfs2_mknod - lock(&ocfs2_file_ip_alloc_sem_key);
.
.
.
ocfs2_get_system_file_inode - lock(&osb->system_file_mutex);

CPU1 -
ocfs2_fill_super - lock(&osb->system_file_mutex);
.
.
.
ocfs2_read_virt_blocks - lock(&ocfs2_file_ip_alloc_sem_key);

This issue can be resolved by making the down_read -> down_read_try
in the ocfs2_read_virt_blocks.

[1] https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd

Link: https://lkml.kernel.org/r/20240924093257.7181-1-pvmohammedanees2003@gmail.com
Signed-off-by: Mohammed Anees <pvmohammedanees2003@...il.com>
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
Reported-by: <syzbot+e0055ea09f1f5e6fabdd@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd
Tested-by: syzbot+e0055ea09f1f5e6fabdd@...kaller.appspotmail.com
Cc: Mark Fasheh <mark@...heh.com>
Cc: Joel Becker <jlbec@...lplan.org>
Cc: Junxiao Bi <junxiao.bi@...cle.com>
Cc: Changwei Ge <gechangwei@...e.cn>
Cc: Gang He <ghe@...e.com>
Cc: Jun Piao <piaojun@...wei.com>
Cc:  <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Dmitriy Privalov <d.privalov@....ru>
---
 fs/ocfs2/extent_map.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 70a768b623cf..f7672472fa82 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -973,7 +973,13 @@ int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr,
 	}
 
 	while (done < nr) {
-		down_read(&OCFS2_I(inode)->ip_alloc_sem);
+		if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) {
+			rc = -EAGAIN;
+			mlog(ML_ERROR,
+				 "Inode #%llu ip_alloc_sem is temporarily unavailable\n",
+				 (unsigned long long)OCFS2_I(inode)->ip_blkno);
+			break;
+		}
 		rc = ocfs2_extent_map_get_blocks(inode, v_block + done,
 						 &p_block, &p_count, NULL);
 		up_read(&OCFS2_I(inode)->ip_alloc_sem);
-- 
2.34.1