From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- block/holder.c | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 block/holder.c (limited to 'block/holder.c') diff --git a/block/holder.c b/block/holder.c new file mode 100644 index 000000000..267beb3dc --- /dev/null +++ b/block/holder.c @@ -0,0 +1,156 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include + +struct bd_holder_disk { + struct list_head list; + struct kobject *holder_dir; + int refcnt; +}; + +static DEFINE_MUTEX(blk_holder_mutex); + +static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev, + struct gendisk *disk) +{ + struct bd_holder_disk *holder; + + list_for_each_entry(holder, &disk->slave_bdevs, list) + if (holder->holder_dir == bdev->bd_holder_dir) + return holder; + return NULL; +} + +static int add_symlink(struct kobject *from, struct kobject *to) +{ + return sysfs_create_link(from, to, kobject_name(to)); +} + +static void del_symlink(struct kobject *from, struct kobject *to) +{ + sysfs_remove_link(from, kobject_name(to)); +} + +/** + * bd_link_disk_holder - create symlinks between holding disk and slave bdev + * @bdev: the claimed slave bdev + * @disk: the holding disk + * + * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. + * + * This functions creates the following sysfs symlinks. + * + * - from "slaves" directory of the holder @disk to the claimed @bdev + * - from "holders" directory of the @bdev to the holder @disk + * + * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is + * passed to bd_link_disk_holder(), then: + * + * /sys/block/dm-0/slaves/sda --> /sys/block/sda + * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0 + * + * The caller must have claimed @bdev before calling this function and + * ensure that both @bdev and @disk are valid during the creation and + * lifetime of these symlinks. + * + * CONTEXT: + * Might sleep. + * + * RETURNS: + * 0 on success, -errno on failure. + */ +int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) +{ + struct bd_holder_disk *holder; + int ret = 0; + + if (WARN_ON_ONCE(!disk->slave_dir)) + return -EINVAL; + + if (bdev->bd_disk == disk) + return -EINVAL; + + /* + * del_gendisk drops the initial reference to bd_holder_dir, so we + * need to keep our own here to allow for cleanup past that point. + */ + mutex_lock(&bdev->bd_disk->open_mutex); + if (!disk_live(bdev->bd_disk)) { + mutex_unlock(&bdev->bd_disk->open_mutex); + return -ENODEV; + } + kobject_get(bdev->bd_holder_dir); + mutex_unlock(&bdev->bd_disk->open_mutex); + + mutex_lock(&blk_holder_mutex); + WARN_ON_ONCE(!bdev->bd_holder); + + holder = bd_find_holder_disk(bdev, disk); + if (holder) { + kobject_put(bdev->bd_holder_dir); + holder->refcnt++; + goto out_unlock; + } + + holder = kzalloc_obj(*holder); + if (!holder) { + ret = -ENOMEM; + goto out_unlock; + } + + INIT_LIST_HEAD(&holder->list); + holder->refcnt = 1; + holder->holder_dir = bdev->bd_holder_dir; + + ret = add_symlink(disk->slave_dir, bdev_kobj(bdev)); + if (ret) + goto out_free_holder; + ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); + if (ret) + goto out_del_symlink; + list_add(&holder->list, &disk->slave_bdevs); + + mutex_unlock(&blk_holder_mutex); + return 0; + +out_del_symlink: + del_symlink(disk->slave_dir, bdev_kobj(bdev)); +out_free_holder: + kfree(holder); +out_unlock: + mutex_unlock(&blk_holder_mutex); + if (ret) + kobject_put(bdev->bd_holder_dir); + return ret; +} +EXPORT_SYMBOL_GPL(bd_link_disk_holder); + +/** + * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder() + * @bdev: the calimed slave bdev + * @disk: the holding disk + * + * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. + * + * CONTEXT: + * Might sleep. + */ +void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) +{ + struct bd_holder_disk *holder; + + if (WARN_ON_ONCE(!disk->slave_dir)) + return; + + mutex_lock(&blk_holder_mutex); + holder = bd_find_holder_disk(bdev, disk); + if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { + del_symlink(disk->slave_dir, bdev_kobj(bdev)); + del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj); + kobject_put(holder->holder_dir); + list_del_init(&holder->list); + kfree(holder); + } + mutex_unlock(&blk_holder_mutex); +} +EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); -- cgit v1.3.1