The patch titled
Subject: ocfs2: fix deadlock in ocfs2_get_system_file_inode
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
ocfs2-fix-deadlock-in-ocfs2_get_system_file_inode.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-fix-deadlock-in-ocfs2_get_system_file_inode.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mohammed Anees <pvmohammedanees2003@xxxxxxxxx>
Subject: ocfs2: fix deadlock in ocfs2_get_system_file_inode
Date: Tue, 24 Sep 2024 09:32:57 +0000
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@xxxxxxxxx
Signed-off-by: Mohammed Anees <pvmohammedanees2003@xxxxxxxxx>
Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Reported-by: <syzbot+e0055ea09f1f5e6fabdd@xxxxxxxxxxxxxxxxxxxxxxxxx>
Closes: https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd
Tested-by: syzbot+e0055ea09f1f5e6fabdd@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Mark Fasheh <mark@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Changwei Ge <gechangwei@xxxxxxx>
Cc: Gang He <ghe@xxxxxxxx>
Cc: Jun Piao <piaojun@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/extent_map.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/fs/ocfs2/extent_map.c~ocfs2-fix-deadlock-in-ocfs2_get_system_file_inode
+++ a/fs/ocfs2/extent_map.c
@@ -973,7 +973,13 @@ int ocfs2_read_virt_blocks(struct inode
}
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);
_
Patches currently in -mm which might be from pvmohammedanees2003@xxxxxxxxx are
ocfs2-fix-deadlock-in-ocfs2_get_system_file_inode.patch
ocfs2-fix-typo-in-comment.patch
