In the Linux kernel, the following vulnerability has been resolved: ocfs2: fix circular locking dependency in ocfs2_init_acl() A lockdep warning indicates a circular locking dependency between `&oi->ip_xattr_sem` and `&journal->j_trans…

Overview

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: fix circular locking dependency in ocfs2_init_acl()

A lockdep warning indicates a circular locking dependency between &oi->ip_xattr_sem and &journal->j_trans_barrier:

WARNING: possible circular locking dependency detected is trying to acquire lock: (&oi->ip_xattr_sem){++++}-{4:4}, at: ocfs2_init_acl+0x2fd/0x7e0 fs/ocfs2/acl.c:367

but task is already holding lock: (&journal->j_trans_barrier){.+.+}-{4:4}, at: ocfs2_start_trans+0x3ab/0x700 fs/ocfs2/journal.c:369

The deadlock involves two code paths: Path 1 (setxattr) where ocfs2_xattr_set() acquires ip_xattr_sem (write) and then starts a transaction, which acquires j_trans_barrier (read); and Path 2 (mkdir/mknod) where ocfs2_mknod() starts a transaction (j_trans_barrier read) and then calls ocfs2_init_acl(), which attempts to acquire ip_xattr_sem (read) on the parent directory to retrieve the default ACL.

Because rw_semaphores are subject to writer priority, a pending writer on j_trans_barrier (e.g., the journal commit thread) can cause Path 1 to block, while Path 2 is blocked waiting for Path 1 to release ip_xattr_sem.

The patch fixes the lock ordering by precomputing the ACL state before starting the OCFS2 transaction, while preserving POSIX ACL storage semantics and the existing inode/security initialization order. By reading the parent directory's default ACL and preparing the new inode's ACLs outside the transaction, ip_xattr_sem is always acquired before j_trans_barrier.

struct ocfs2_acl_state encapsulates the prepared ACL state, while ocfs2_acl_init_prepare() and ocfs2_acl_init_release() avoid code duplication between ocfs2_mknod() and ocfs2_init_security_and_acl(). ocfs2_calc_xattr_init() and ocfs2_init_acl() use this precomputed state, removing internal ip_xattr_sem acquisition and redundant disk reads.

Additionally, remove the ip_xattr_sem acquisition from ocfs2_xattr_set_handle(). This function is only used while initializing a new inode that has not yet been inserted into the inode hash or attached to a dentry, meaning there is no risk of concurrent access and the lock is unnecessary.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.