Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 443 insertions, 0 deletions

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 000000000..00cc81220
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,443 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Ram backed block device driver.
+ *
+ * Copyright (C) 2007 Nick Piggin
+ * Copyright (C) 2007 Novell Inc.
+ *
+ * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
+ * of their respective owners.
+ */
+
+#include <linux/init.h>
+#include <linux/initrd.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/major.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/highmem.h>
+#include <linux/mutex.h>
+#include <linux/pagemap.h>
+#include <linux/xarray.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#include <linux/debugfs.h>
+
+#include <linux/uaccess.h>
+
+/*
+ * Each block ramdisk device has a xarray brd_pages of pages that stores
+ * the pages containing the block device's contents.
+ */
+struct brd_device {
+	int			brd_number;
+	struct gendisk		*brd_disk;
+	struct list_head	brd_list;
+
+	/*
+	 * Backing store of pages. This is the contents of the block device.
+	 */
+	struct xarray	        brd_pages;
+	u64			brd_nr_pages;
+};
+
+/*
+ * Look up and return a brd's page with reference grabbed for a given sector.
+ */
+static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
+{
+	struct page *page;
+	XA_STATE(xas, &brd->brd_pages, sector >> PAGE_SECTORS_SHIFT);
+
+	rcu_read_lock();
+repeat:
+	page = xas_load(&xas);
+	if (xas_retry(&xas, page)) {
+		xas_reset(&xas);
+		goto repeat;
+	}
+
+	if (!page)
+		goto out;
+
+	if (!get_page_unless_zero(page)) {
+		xas_reset(&xas);
+		goto repeat;
+	}
+
+	if (unlikely(page != xas_reload(&xas))) {
+		put_page(page);
+		xas_reset(&xas);
+		goto repeat;
+	}
+out:
+	rcu_read_unlock();
+
+	return page;
+}
+
+/*
+ * Insert a new page for a given sector, if one does not already exist.
+ * The returned page will grab reference.
+ */
+static struct page *brd_insert_page(struct brd_device *brd, sector_t sector,
+		blk_opf_t opf)
+{
+	gfp_t gfp = (opf & REQ_NOWAIT) ? GFP_NOWAIT : GFP_NOIO;
+	struct page *page, *ret;
+
+	page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM);
+	if (!page)
+		return ERR_PTR(-ENOMEM);
+
+	xa_lock(&brd->brd_pages);
+	ret = __xa_cmpxchg(&brd->brd_pages, sector >> PAGE_SECTORS_SHIFT, NULL,
+			page, gfp);
+	if (!ret) {
+		brd->brd_nr_pages++;
+		get_page(page);
+		xa_unlock(&brd->brd_pages);
+		return page;
+	}
+
+	if (!xa_is_err(ret)) {
+		get_page(ret);
+		xa_unlock(&brd->brd_pages);
+		put_page(page);
+		return ret;
+	}
+
+	xa_unlock(&brd->brd_pages);
+	put_page(page);
+	return ERR_PTR(xa_err(ret));
+}
+
+/*
+ * Free all backing store pages and xarray. This must only be called when
+ * there are no other users of the device.
+ */
+static void brd_free_pages(struct brd_device *brd)
+{
+	struct page *page;
+	pgoff_t idx;
+
+	xa_for_each(&brd->brd_pages, idx, page) {
+		put_page(page);
+		cond_resched();
+	}
+
+	xa_destroy(&brd->brd_pages);
+}
+
+/*
+ * Process a single segment.  The segment is capped to not cross page boundaries
+ * in both the bio and the brd backing memory.
+ */
+static bool brd_rw_bvec(struct brd_device *brd, struct bio *bio)
+{
+	struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
+	sector_t sector = bio->bi_iter.bi_sector;
+	u32 offset = (sector & (PAGE_SECTORS - 1)) << SECTOR_SHIFT;
+	blk_opf_t opf = bio->bi_opf;
+	struct page *page;
+	void *kaddr;
+
+	bv.bv_len = min_t(u32, bv.bv_len, PAGE_SIZE - offset);
+
+	page = brd_lookup_page(brd, sector);
+	if (!page && op_is_write(opf)) {
+		page = brd_insert_page(brd, sector, opf);
+		if (IS_ERR(page))
+			goto out_error;
+	}
+
+	kaddr = bvec_kmap_local(&bv);
+	if (op_is_write(opf)) {
+		memcpy_to_page(page, offset, kaddr, bv.bv_len);
+	} else {
+		if (page)
+			memcpy_from_page(kaddr, page, offset, bv.bv_len);
+		else
+			memset(kaddr, 0, bv.bv_len);
+	}
+	kunmap_local(kaddr);
+
+	bio_advance_iter_single(bio, &bio->bi_iter, bv.bv_len);
+	if (page)
+		put_page(page);
+	return true;
+
+out_error:
+	if (PTR_ERR(page) == -ENOMEM && (opf & REQ_NOWAIT))
+		bio_wouldblock_error(bio);
+	else
+		bio_io_error(bio);
+	return false;
+}
+
+static void brd_do_discard(struct brd_device *brd, sector_t sector, u32 size)
+{
+	sector_t aligned_sector = round_up(sector, PAGE_SECTORS);
+	sector_t aligned_end = round_down(
+			sector + (size >> SECTOR_SHIFT), PAGE_SECTORS);
+	struct page *page;
+
+	if (aligned_end <= aligned_sector)
+		return;
+
+	xa_lock(&brd->brd_pages);
+	while (aligned_sector < aligned_end && aligned_sector < rd_size * 2) {
+		page = __xa_erase(&brd->brd_pages, aligned_sector >> PAGE_SECTORS_SHIFT);
+		if (page) {
+			put_page(page);
+			brd->brd_nr_pages--;
+		}
+		aligned_sector += PAGE_SECTORS;
+	}
+	xa_unlock(&brd->brd_pages);
+}
+
+static void brd_submit_bio(struct bio *bio)
+{
+	struct brd_device *brd = bio->bi_bdev->bd_disk->private_data;
+
+	if (unlikely(op_is_discard(bio->bi_opf))) {
+		brd_do_discard(brd, bio->bi_iter.bi_sector,
+				bio->bi_iter.bi_size);
+		bio_endio(bio);
+		return;
+	}
+
+	do {
+		if (!brd_rw_bvec(brd, bio))
+			return;
+	} while (bio->bi_iter.bi_size);
+
+	bio_endio(bio);
+}
+
+static const struct block_device_operations brd_fops = {
+	.owner =		THIS_MODULE,
+	.submit_bio =		brd_submit_bio,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
+module_param(rd_nr, int, 0444);
+MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
+
+unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_size, ulong, 0444);
+MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+
+static int max_part = 1;
+module_param(max_part, int, 0444);
+MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
+
+MODULE_DESCRIPTION("Ram backed block device driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
+MODULE_ALIAS("rd");
+
+#ifndef MODULE
+/* Legacy boot options - nonmodular */
+static int __init ramdisk_size(char *str)
+{
+	return kstrtoul(str, 0, &rd_size) == 0;
+}
+__setup("ramdisk_size=", ramdisk_size);
+#endif
+
+/*
+ * The device scheme is derived from loop.c. Keep them in synch where possible
+ * (should share code eventually).
+ */
+static LIST_HEAD(brd_devices);
+static DEFINE_MUTEX(brd_devices_mutex);
+static struct dentry *brd_debugfs_dir;
+
+static struct brd_device *brd_find_or_alloc_device(int i)
+{
+	struct brd_device *brd;
+
+	mutex_lock(&brd_devices_mutex);
+	list_for_each_entry(brd, &brd_devices, brd_list) {
+		if (brd->brd_number == i) {
+			mutex_unlock(&brd_devices_mutex);
+			return ERR_PTR(-EEXIST);
+		}
+	}
+
+	brd = kzalloc_obj(*brd);
+	if (!brd) {
+		mutex_unlock(&brd_devices_mutex);
+		return ERR_PTR(-ENOMEM);
+	}
+	brd->brd_number	= i;
+	list_add_tail(&brd->brd_list, &brd_devices);
+	mutex_unlock(&brd_devices_mutex);
+	return brd;
+}
+
+static void brd_free_device(struct brd_device *brd)
+{
+	mutex_lock(&brd_devices_mutex);
+	list_del(&brd->brd_list);
+	mutex_unlock(&brd_devices_mutex);
+	kfree(brd);
+}
+
+static int brd_alloc(int i)
+{
+	struct brd_device *brd;
+	struct gendisk *disk;
+	char buf[DISK_NAME_LEN];
+	int err = -ENOMEM;
+	struct queue_limits lim = {
+		/*
+		 * This is so fdisk will align partitions on 4k, because of
+		 * direct_access API needing 4k alignment, returning a PFN
+		 * (This is only a problem on very small devices <= 4M,
+		 *  otherwise fdisk will align on 1M. Regardless this call
+		 *  is harmless)
+		 */
+		.physical_block_size	= PAGE_SIZE,
+		.max_hw_discard_sectors	= UINT_MAX,
+		.max_discard_segments	= 1,
+		.discard_granularity	= PAGE_SIZE,
+		.features		= BLK_FEAT_SYNCHRONOUS |
+					  BLK_FEAT_NOWAIT,
+	};
+
+	brd = brd_find_or_alloc_device(i);
+	if (IS_ERR(brd))
+		return PTR_ERR(brd);
+
+	xa_init(&brd->brd_pages);
+
+	snprintf(buf, DISK_NAME_LEN, "ram%d", i);
+	if (!IS_ERR_OR_NULL(brd_debugfs_dir))
+		debugfs_create_u64(buf, 0444, brd_debugfs_dir,
+				&brd->brd_nr_pages);
+
+	disk = brd->brd_disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
+	if (IS_ERR(disk)) {
+		err = PTR_ERR(disk);
+		goto out_free_dev;
+	}
+	disk->major		= RAMDISK_MAJOR;
+	disk->first_minor	= i * max_part;
+	disk->minors		= max_part;
+	disk->fops		= &brd_fops;
+	disk->private_data	= brd;
+	strscpy(disk->disk_name, buf, DISK_NAME_LEN);
+	set_capacity(disk, rd_size * 2);
+	
+	err = add_disk(disk);
+	if (err)
+		goto out_cleanup_disk;
+
+	return 0;
+
+out_cleanup_disk:
+	put_disk(disk);
+out_free_dev:
+	brd_free_device(brd);
+	return err;
+}
+
+static void brd_probe(dev_t dev)
+{
+	brd_alloc(MINOR(dev) / max_part);
+}
+
+static void brd_cleanup(void)
+{
+	struct brd_device *brd, *next;
+
+	debugfs_remove_recursive(brd_debugfs_dir);
+
+	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+		del_gendisk(brd->brd_disk);
+		put_disk(brd->brd_disk);
+		brd_free_pages(brd);
+		brd_free_device(brd);
+	}
+}
+
+static inline void brd_check_and_reset_par(void)
+{
+	if (unlikely(!max_part))
+		max_part = 1;
+
+	/*
+	 * make sure 'max_part' can be divided exactly by (1U << MINORBITS),
+	 * otherwise, it is possiable to get same dev_t when adding partitions.
+	 */
+	if ((1U << MINORBITS) % max_part != 0)
+		max_part = 1UL << fls(max_part);
+
+	if (max_part > DISK_MAX_PARTS) {
+		pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n",
+			DISK_MAX_PARTS, DISK_MAX_PARTS);
+		max_part = DISK_MAX_PARTS;
+	}
+}
+
+static int __init brd_init(void)
+{
+	int err, i;
+
+	/*
+	 * brd module now has a feature to instantiate underlying device
+	 * structure on-demand, provided that there is an access dev node.
+	 *
+	 * (1) if rd_nr is specified, create that many upfront. else
+	 *     it defaults to CONFIG_BLK_DEV_RAM_COUNT
+	 * (2) User can further extend brd devices by create dev node themselves
+	 *     and have kernel automatically instantiate actual device
+	 *     on-demand. Example:
+	 *		mknod /path/devnod_name b 1 X	# 1 is the rd major
+	 *		fdisk -l /path/devnod_name
+	 *	If (X / max_part) was not already created it will be created
+	 *	dynamically.
+	 */
+
+	brd_check_and_reset_par();
+
+	brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
+
+	if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {
+		err = -EIO;
+		goto out_free;
+	}
+
+	for (i = 0; i < rd_nr; i++)
+		brd_alloc(i);
+
+	pr_info("brd: module loaded\n");
+	return 0;
+
+out_free:
+	brd_cleanup();
+
+	pr_info("brd: module NOT loaded !!!\n");
+	return err;
+}
+
+static void __exit brd_exit(void)
+{
+
+	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+	brd_cleanup();
+
+	pr_info("brd: module unloaded\n");
+}
+
+module_init(brd_init);
+module_exit(brd_exit);
+