5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yun Zhou commit 9dbf74f4022f80f7669d2b3c22c5deb46c1b5674 upstream. usbg_make_tpg() held dep_lock while calling configfs_depend_item_unlocked(), which acquires the configfs root inode lock when operating across subsystems. This creates a circular lock dependency with configfs_rmdir(): dep_lock -> configfs root inode lock -> su_mutex -> dep_lock In usbg_make_tpg(), dep_lock only serialized the read of opts->ready, which is a monotonic flag that transitions from false to true exactly once (in tcm_set_name()) and never reverts. Remove dep_lock from usbg_make_tpg() entirely and use READ_ONCE/WRITE_ONCE to access opts->ready locklessly instead. Reported-by: syzbot+c9f9d646b08f3b6032fe@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c9f9d646b08f3b6032fe Fixes: 4bb8548df632 ("usb: gadget: f_tcm: add configfs support") Cc: stable@vger.kernel.org Signed-off-by: Yun Zhou Link: https://patch.msgid.link/20260731081151.285599-1-yun.zhou@windriver.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_tcm.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) --- a/drivers/usb/gadget/function/f_tcm.c +++ b/drivers/usb/gadget/function/f_tcm.c @@ -1358,19 +1358,25 @@ static struct se_portal_group *usbg_make opts = container_of(tpg_instances[i].func_inst, struct f_tcm_opts, func_inst); - mutex_lock(&opts->dep_lock); - if (!opts->ready) - goto unlock_dep; + if (!READ_ONCE(opts->ready)) + goto unlock_inst; if (opts->has_dep) { if (!try_module_get(opts->dependent)) - goto unlock_dep; + goto unlock_inst; } else { + /* + * configfs_depend_item_unlocked() may acquire the configfs + * root inode lock when the target belongs to a different + * subsystem. Calling it under dep_lock would create a + * circular dependency: + * dep_lock -> configfs inode lock -> su_mutex -> dep_lock + */ ret = configfs_depend_item_unlocked( wwn->wwn_group.cg_subsys, &opts->func_inst.group.cg_item); if (ret) - goto unlock_dep; + goto unlock_inst; } tpg = kzalloc(sizeof(struct usbg_tpg), GFP_KERNEL); @@ -1396,7 +1402,6 @@ static struct se_portal_group *usbg_make tpg_instances[i].tpg = tpg; tpg->fi = tpg_instances[i].func_inst; - mutex_unlock(&opts->dep_lock); mutex_unlock(&tpg_instances_lock); return &tpg->se_tpg; @@ -1409,8 +1414,6 @@ unref_dep: module_put(opts->dependent); else configfs_undepend_item_unlocked(&opts->func_inst.group.cg_item); -unlock_dep: - mutex_unlock(&opts->dep_lock); unlock_inst: mutex_unlock(&tpg_instances_lock); @@ -2368,9 +2371,7 @@ static int tcm_set_name(struct usb_funct pr_debug("tcm: Activating %s\n", name); - mutex_lock(&opts->dep_lock); - opts->ready = true; - mutex_unlock(&opts->dep_lock); + WRITE_ONCE(opts->ready, true); return 0; }