From e062baf5680845705d21df415c8f0751c96b0792 Mon Sep 17 00:00:00 2001 From: Cen Zhang Date: Tue, 13 Oct 2026 09:58:58 +0800 Subject: [PATCH] ocfs2: publish the filecheck owner before adding sysfs attributes ocfs2_filecheck_create_sysfs() initializes the filecheck allocation before calling kobject_init_and_add(), but assigns entry->fs_fcheck only after that call returns. The default attribute group can already be visible while registration is in progress. A concurrent read can therefore enter ocfs2_filecheck_attr_show() with a NULL fs_fcheck and try to lock its fc_lock. Assign the initialized owner before adding the kobject, so every activated attribute has valid state. Clear the pointer when addition fails, preserving the existing teardown guard and error cleanup. A controlled probe-instrumented test kernel with the original OCFS2 registration ordering produced this Oops during a concurrent sysfs read: KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] RIP: 0010:kasan_byte_accessible+0x15/0x30 Call Trace: __kasan_check_byte+0x13/0x50 lock_acquire+0x113/0x300 _raw_spin_lock+0x31/0x40 ocfs2_filecheck_attr_show+0x138/0x5f0 ocfs2_filecheck_show+0x5d/0x90 sysfs_kf_seq_show+0x1d3/0x360 seq_read_iter+0x480/0x1110 kernfs_fop_read_iter+0x419/0x5a0 vfs_read+0x7d2/0xc20 ksys_read+0x111/0x200 do_syscall_64+0x114/0x620 entry_SYSCALL_64_after_hwframe+0x77/0x7f Modules linked in: Link: https://lore.kernel.org/pm-ocfs2-objects-candidate-0086-v4-1b3a3c5fd05c1fb41df9@gmail.com Fixes: 5f483c4abb50 ("ocfs2: add kobject for online file check") Signed-off-by: Cen Zhang Signed-off-by: Andrew Morton Reviewed-by: Heming Zhao Reviewed-by: Joseph Qi Assisted-by: LLM Cc: Mark Fasheh Cc: Joel Becker Cc: Gang He Cc: Jia-Ju Bai Cc: Cc: --- fs/ocfs2/filecheck.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/filecheck.c b/fs/ocfs2/filecheck.c index be713d7d24a7..75334e4bd082 100644 --- a/fs/ocfs2/filecheck.c +++ b/fs/ocfs2/filecheck.c @@ -179,17 +179,20 @@ int ocfs2_filecheck_create_sysfs(struct ocfs2_super *osb) fcheck->fc_size = 0; fcheck->fc_done = 0; + /* Publish the initialized owner before activating its sysfs callbacks. */ + entry->fs_fcheck = fcheck; entry->fs_kobj.kset = osb->osb_dev_kset; init_completion(&entry->fs_kobj_unregister); ret = kobject_init_and_add(&entry->fs_kobj, &ocfs2_ktype_filecheck, NULL, "filecheck"); if (ret) { + /* Mount failure still calls ocfs2_filecheck_remove_sysfs(). */ + entry->fs_fcheck = NULL; kobject_put(&entry->fs_kobj); kfree(fcheck); return ret; } - entry->fs_fcheck = fcheck; return 0; }