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...

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@gmail.com 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@gmail.co... Signed-off-by: Mohammed Anees pvmohammedanees2003@gmail.com Reviewed-by: Joseph Qi joseph.qi@linux.alibaba.com Reported-by: syzbot+e0055ea09f1f5e6fabdd@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd Tested-by: syzbot+e0055ea09f1f5e6fabdd@syzkaller.appspotmail.com Cc: Mark Fasheh mark@fasheh.com Cc: Joel Becker jlbec@evilplan.org Cc: Junxiao Bi junxiao.bi@oracle.com Cc: Changwei Ge gechangwei@live.cn Cc: Gang He ghe@suse.com Cc: Jun Piao piaojun@huawei.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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@gmail.com are

ocfs2-fix-deadlock-in-ocfs2_get_system_file_inode.patch ocfs2-fix-typo-in-comment.patch