x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 662 insertions, 0 deletions

diff --git a/fs/ext4/orphan.c b/fs/ext4/orphan.c
new file mode 100644
index 000000000..b4675aa7e
--- /dev/null
+++ b/fs/ext4/orphan.c
@@ -0,0 +1,662 @@
+/*
+ * Ext4 orphan inode handling
+ */
+#include <linux/fs.h>
+#include <linux/quotaops.h>
+#include <linux/buffer_head.h>
+#include <linux/string_choices.h>
+
+#include "ext4.h"
+#include "ext4_jbd2.h"
+
+#define EXT4_MAX_ORPHAN_FILE_BLOCKS 512
+
+static int ext4_orphan_file_add(handle_t *handle, struct inode *inode)
+{
+	int i, j, start;
+	struct ext4_orphan_info *oi = &EXT4_SB(inode->i_sb)->s_orphan_info;
+	int ret = 0;
+	bool found = false;
+	__le32 *bdata;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(inode->i_sb);
+	int looped = 0;
+
+	/*
+	 * Find block with free orphan entry. Use CPU number for a naive hash
+	 * for a search start in the orphan file
+	 */
+	start = raw_smp_processor_id()*13 % oi->of_blocks;
+	i = start;
+	do {
+		if (atomic_dec_if_positive(&oi->of_binfo[i].ob_free_entries)
+		    >= 0) {
+			found = true;
+			break;
+		}
+		if (++i >= oi->of_blocks)
+			i = 0;
+	} while (i != start);
+
+	if (!found) {
+		/*
+		 * For now we don't grow or shrink orphan file. We just use
+		 * whatever was allocated at mke2fs time. The additional
+		 * credits we would have to reserve for each orphan inode
+		 * operation just don't seem worth it.
+		 */
+		return -ENOSPC;
+	}
+
+	ret = ext4_journal_get_write_access(handle, inode->i_sb,
+				oi->of_binfo[i].ob_bh, EXT4_JTR_ORPHAN_FILE);
+	if (ret) {
+		atomic_inc(&oi->of_binfo[i].ob_free_entries);
+		return ret;
+	}
+
+	bdata = (__le32 *)(oi->of_binfo[i].ob_bh->b_data);
+	/* Find empty slot in a block */
+	j = 0;
+	do {
+		if (looped) {
+			/*
+			 * Did we walk through the block several times without
+			 * finding free entry? It is theoretically possible
+			 * if entries get constantly allocated and freed or
+			 * if the block is corrupted. Avoid indefinite looping
+			 * and bail. We'll use orphan list instead.
+			 */
+			if (looped > 3) {
+				atomic_inc(&oi->of_binfo[i].ob_free_entries);
+				return -ENOSPC;
+			}
+			cond_resched();
+		}
+		while (bdata[j]) {
+			if (++j >= inodes_per_ob) {
+				j = 0;
+				looped++;
+			}
+		}
+	} while (cmpxchg(&bdata[j], (__le32)0, cpu_to_le32(inode->i_ino)) !=
+		 (__le32)0);
+
+	EXT4_I(inode)->i_orphan_idx = i * inodes_per_ob + j;
+	ext4_set_inode_state(inode, EXT4_STATE_ORPHAN_FILE);
+
+	return ext4_handle_dirty_metadata(handle, NULL, oi->of_binfo[i].ob_bh);
+}
+
+/*
+ * ext4_orphan_add() links an unlinked or truncated inode into a list of
+ * such inodes, starting at the superblock, in case we crash before the
+ * file is closed/deleted, or in case the inode truncate spans multiple
+ * transactions and the last transaction is not recovered after a crash.
+ *
+ * At filesystem recovery time, we walk this list deleting unlinked
+ * inodes and truncating linked inodes in ext4_orphan_cleanup().
+ *
+ * Orphan list manipulation functions must be called under i_rwsem unless
+ * we are just creating the inode or deleting it.
+ */
+int ext4_orphan_add(handle_t *handle, struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_iloc iloc;
+	int err = 0, rc;
+	bool dirty = false;
+
+	if (!sbi->s_journal || is_bad_inode(inode))
+		return 0;
+
+	WARN_ON_ONCE(!(inode_state_read_once(inode) & (I_NEW | I_FREEING)) &&
+		     !inode_is_locked(inode));
+	if (ext4_inode_orphan_tracked(inode))
+		return 0;
+
+	/*
+	 * Orphan handling is only valid for files with data blocks
+	 * being truncated, or files being unlinked. Note that we either
+	 * hold i_rwsem, or the inode can not be referenced from outside,
+	 * so i_nlink should not be bumped due to race
+	 */
+	ASSERT((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+		  S_ISLNK(inode->i_mode)) || inode->i_nlink == 0);
+
+	if (sbi->s_orphan_info.of_blocks) {
+		err = ext4_orphan_file_add(handle, inode);
+		/*
+		 * Fallback to normal orphan list of orphan file is
+		 * out of space
+		 */
+		if (err != -ENOSPC)
+			return err;
+	}
+
+	BUFFER_TRACE(sbi->s_sbh, "get_write_access");
+	err = ext4_journal_get_write_access(handle, sb, sbi->s_sbh,
+					    EXT4_JTR_NONE);
+	if (err)
+		goto out;
+
+	err = ext4_reserve_inode_write(handle, inode, &iloc);
+	if (err)
+		goto out;
+
+	mutex_lock(&sbi->s_orphan_lock);
+	/*
+	 * Due to previous errors inode may be already a part of on-disk
+	 * orphan list. If so skip on-disk list modification.
+	 */
+	if (!NEXT_ORPHAN(inode) || NEXT_ORPHAN(inode) >
+	    (le32_to_cpu(sbi->s_es->s_inodes_count))) {
+		/* Insert this inode at the head of the on-disk orphan list */
+		NEXT_ORPHAN(inode) = le32_to_cpu(sbi->s_es->s_last_orphan);
+		lock_buffer(sbi->s_sbh);
+		sbi->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
+		ext4_superblock_csum_set(sb);
+		unlock_buffer(sbi->s_sbh);
+		dirty = true;
+	}
+	list_add(&EXT4_I(inode)->i_orphan, &sbi->s_orphan);
+	mutex_unlock(&sbi->s_orphan_lock);
+
+	if (dirty) {
+		err = ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
+		rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
+		if (!err)
+			err = rc;
+		if (err) {
+			/*
+			 * We have to remove inode from in-memory list if
+			 * addition to on disk orphan list failed. Stray orphan
+			 * list entries can cause panics at unmount time.
+			 */
+			mutex_lock(&sbi->s_orphan_lock);
+			list_del_init(&EXT4_I(inode)->i_orphan);
+			mutex_unlock(&sbi->s_orphan_lock);
+		}
+	} else
+		brelse(iloc.bh);
+
+	ext4_debug("superblock will point to %llu\n", inode->i_ino);
+	ext4_debug("orphan inode %llu will point to %d\n",
+			inode->i_ino, NEXT_ORPHAN(inode));
+out:
+	ext4_std_error(sb, err);
+	return err;
+}
+
+static int ext4_orphan_file_del(handle_t *handle, struct inode *inode)
+{
+	struct ext4_orphan_info *oi = &EXT4_SB(inode->i_sb)->s_orphan_info;
+	__le32 *bdata;
+	int blk, off;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(inode->i_sb);
+	int ret = 0;
+
+	if (!handle)
+		goto out;
+	blk = EXT4_I(inode)->i_orphan_idx / inodes_per_ob;
+	off = EXT4_I(inode)->i_orphan_idx % inodes_per_ob;
+	if (WARN_ON_ONCE(blk >= oi->of_blocks))
+		goto out;
+
+	ret = ext4_journal_get_write_access(handle, inode->i_sb,
+				oi->of_binfo[blk].ob_bh, EXT4_JTR_ORPHAN_FILE);
+	if (ret)
+		goto out;
+
+	bdata = (__le32 *)(oi->of_binfo[blk].ob_bh->b_data);
+	bdata[off] = 0;
+	atomic_inc(&oi->of_binfo[blk].ob_free_entries);
+	ret = ext4_handle_dirty_metadata(handle, NULL, oi->of_binfo[blk].ob_bh);
+out:
+	ext4_clear_inode_state(inode, EXT4_STATE_ORPHAN_FILE);
+	INIT_LIST_HEAD(&EXT4_I(inode)->i_orphan);
+
+	return ret;
+}
+
+/*
+ * ext4_orphan_del() removes an unlinked or truncated inode from the list
+ * of such inodes stored on disk, because it is finally being cleaned up.
+ */
+int ext4_orphan_del(handle_t *handle, struct inode *inode)
+{
+	struct list_head *prev;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	__u32 ino_next;
+	struct ext4_iloc iloc;
+	int err = 0;
+
+	if (!sbi->s_journal && !(sbi->s_mount_state & EXT4_ORPHAN_FS))
+		return 0;
+
+	WARN_ON_ONCE(!(inode_state_read_once(inode) & (I_NEW | I_FREEING)) &&
+		     !inode_is_locked(inode));
+	if (ext4_test_inode_state(inode, EXT4_STATE_ORPHAN_FILE))
+		return ext4_orphan_file_del(handle, inode);
+
+	/* Do this quick check before taking global s_orphan_lock. */
+	if (list_empty(&ei->i_orphan))
+		return 0;
+
+	if (handle) {
+		/* Grab inode buffer early before taking global s_orphan_lock */
+		err = ext4_reserve_inode_write(handle, inode, &iloc);
+	}
+
+	mutex_lock(&sbi->s_orphan_lock);
+	ext4_debug("remove inode %llu from orphan list\n", inode->i_ino);
+
+	prev = ei->i_orphan.prev;
+	list_del_init(&ei->i_orphan);
+
+	/* If we're on an error path, we may not have a valid
+	 * transaction handle with which to update the orphan list on
+	 * disk, but we still need to remove the inode from the linked
+	 * list in memory. */
+	if (!handle || err) {
+		mutex_unlock(&sbi->s_orphan_lock);
+		goto out_err;
+	}
+
+	ino_next = NEXT_ORPHAN(inode);
+	if (prev == &sbi->s_orphan) {
+		ext4_debug("superblock will point to %u\n", ino_next);
+		BUFFER_TRACE(sbi->s_sbh, "get_write_access");
+		err = ext4_journal_get_write_access(handle, inode->i_sb,
+						    sbi->s_sbh, EXT4_JTR_NONE);
+		if (err) {
+			mutex_unlock(&sbi->s_orphan_lock);
+			goto out_brelse;
+		}
+		lock_buffer(sbi->s_sbh);
+		sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
+		ext4_superblock_csum_set(inode->i_sb);
+		unlock_buffer(sbi->s_sbh);
+		mutex_unlock(&sbi->s_orphan_lock);
+		err = ext4_handle_dirty_metadata(handle, NULL, sbi->s_sbh);
+	} else {
+		struct ext4_iloc iloc2;
+		struct inode *i_prev =
+			&list_entry(prev, struct ext4_inode_info, i_orphan)->vfs_inode;
+
+		ext4_debug("orphan inode %llu will point to %u\n",
+			  i_prev->i_ino, ino_next);
+		err = ext4_reserve_inode_write(handle, i_prev, &iloc2);
+		if (err) {
+			mutex_unlock(&sbi->s_orphan_lock);
+			goto out_brelse;
+		}
+		NEXT_ORPHAN(i_prev) = ino_next;
+		err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
+		mutex_unlock(&sbi->s_orphan_lock);
+	}
+	if (err)
+		goto out_brelse;
+	NEXT_ORPHAN(inode) = 0;
+	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
+out_err:
+	ext4_std_error(inode->i_sb, err);
+	return err;
+
+out_brelse:
+	brelse(iloc.bh);
+	goto out_err;
+}
+
+#ifdef CONFIG_QUOTA
+static int ext4_quota_on_mount(struct super_block *sb, int type)
+{
+	return dquot_quota_on_mount(sb,
+		rcu_dereference_protected(EXT4_SB(sb)->s_qf_names[type],
+					  lockdep_is_held(&sb->s_umount)),
+		EXT4_SB(sb)->s_jquota_fmt, type);
+}
+#endif
+
+static void ext4_process_orphan(struct inode *inode,
+				int *nr_truncates, int *nr_orphans)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret;
+
+	dquot_initialize(inode);
+	if (inode->i_nlink) {
+		if (test_opt(sb, DEBUG))
+			ext4_msg(sb, KERN_DEBUG,
+				"%s: truncating inode %llu to %lld bytes",
+				__func__, inode->i_ino, inode->i_size);
+		ext4_debug("truncating inode %llu to %lld bytes\n",
+			   inode->i_ino, inode->i_size);
+		inode_lock(inode);
+		truncate_inode_pages(inode->i_mapping, inode->i_size);
+		ret = ext4_truncate(inode);
+		if (ret) {
+			/*
+			 * We need to clean up the in-core orphan list
+			 * manually if ext4_truncate() failed to get a
+			 * transaction handle.
+			 */
+			ext4_orphan_del(NULL, inode);
+			ext4_std_error(inode->i_sb, ret);
+		}
+		inode_unlock(inode);
+		(*nr_truncates)++;
+	} else {
+		if (test_opt(sb, DEBUG))
+			ext4_msg(sb, KERN_DEBUG,
+				"%s: deleting unreferenced inode %llu",
+				__func__, inode->i_ino);
+		ext4_debug("deleting unreferenced inode %llu\n",
+			   inode->i_ino);
+		(*nr_orphans)++;
+	}
+	iput(inode);  /* The delete magic happens here! */
+}
+
+/* ext4_orphan_cleanup() walks a singly-linked list of inodes (starting at
+ * the superblock) which were deleted from all directories, but held open by
+ * a process at the time of a crash.  We walk the list and try to delete these
+ * inodes at recovery time (only with a read-write filesystem).
+ *
+ * In order to keep the orphan inode chain consistent during traversal (in
+ * case of crash during recovery), we link each inode into the superblock
+ * orphan list_head and handle it the same way as an inode deletion during
+ * normal operation (which journals the operations for us).
+ *
+ * We only do an iget() and an iput() on each inode, which is very safe if we
+ * accidentally point at an in-use or already deleted inode.  The worst that
+ * can happen in this case is that we get a "bit already cleared" message from
+ * ext4_free_inode().  The only reason we would point at a wrong inode is if
+ * e2fsck was run on this filesystem, and it must have already done the orphan
+ * inode cleanup for us, so we can safely abort without any further action.
+ */
+void ext4_orphan_cleanup(struct super_block *sb, struct ext4_super_block *es)
+{
+	unsigned int s_flags = sb->s_flags;
+	int nr_orphans = 0, nr_truncates = 0;
+	struct inode *inode;
+	int i, j;
+#ifdef CONFIG_QUOTA
+	int quota_update = 0;
+#endif
+	__le32 *bdata;
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
+
+	if (!es->s_last_orphan && ext4_orphan_file_empty(sb)) {
+		ext4_debug("no orphan inodes to clean up\n");
+		return;
+	}
+
+	if (bdev_read_only(sb->s_bdev)) {
+		ext4_msg(sb, KERN_ERR, "write access "
+			"unavailable, skipping orphan cleanup");
+		return;
+	}
+
+	/* Check if feature set would not allow a r/w mount */
+	if (!ext4_feature_set_ok(sb, 0)) {
+		ext4_msg(sb, KERN_INFO, "Skipping orphan cleanup due to "
+			 "unknown ROCOMPAT features");
+		return;
+	}
+
+	if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
+		/* don't clear list on RO mount w/ errors */
+		if (es->s_last_orphan && !(s_flags & SB_RDONLY)) {
+			ext4_msg(sb, KERN_INFO, "Errors on filesystem, "
+				  "clearing orphan list.");
+			es->s_last_orphan = 0;
+		}
+		ext4_debug("Skipping orphan recovery on fs with errors.\n");
+		return;
+	}
+
+	if (s_flags & SB_RDONLY) {
+		ext4_msg(sb, KERN_INFO, "orphan cleanup on readonly fs");
+		sb->s_flags &= ~SB_RDONLY;
+	}
+#ifdef CONFIG_QUOTA
+	/*
+	 * Turn on quotas which were not enabled for read-only mounts if
+	 * filesystem has quota feature, so that they are updated correctly.
+	 */
+	if (ext4_has_feature_quota(sb) && (s_flags & SB_RDONLY)) {
+		int ret = ext4_enable_quotas(sb);
+
+		if (!ret)
+			quota_update = 1;
+		else
+			ext4_msg(sb, KERN_ERR,
+				"Cannot turn on quotas: error %d", ret);
+	}
+
+	/* Turn on journaled quotas used for old sytle */
+	for (i = 0; i < EXT4_MAXQUOTAS; i++) {
+		if (EXT4_SB(sb)->s_qf_names[i]) {
+			int ret = ext4_quota_on_mount(sb, i);
+
+			if (!ret)
+				quota_update = 1;
+			else
+				ext4_msg(sb, KERN_ERR,
+					"Cannot turn on journaled "
+					"quota: type %d: error %d", i, ret);
+		}
+	}
+#endif
+
+	while (es->s_last_orphan) {
+		/*
+		 * We may have encountered an error during cleanup; if
+		 * so, skip the rest.
+		 */
+		if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
+			ext4_debug("Skipping orphan recovery on fs with errors.\n");
+			es->s_last_orphan = 0;
+			break;
+		}
+
+		inode = ext4_orphan_get(sb, le32_to_cpu(es->s_last_orphan));
+		if (IS_ERR(inode)) {
+			es->s_last_orphan = 0;
+			break;
+		}
+
+		list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
+		ext4_process_orphan(inode, &nr_truncates, &nr_orphans);
+	}
+
+	for (i = 0; i < oi->of_blocks; i++) {
+		bdata = (__le32 *)(oi->of_binfo[i].ob_bh->b_data);
+		for (j = 0; j < inodes_per_ob; j++) {
+			if (!bdata[j])
+				continue;
+			inode = ext4_orphan_get(sb, le32_to_cpu(bdata[j]));
+			if (IS_ERR(inode))
+				continue;
+			ext4_set_inode_state(inode, EXT4_STATE_ORPHAN_FILE);
+			EXT4_I(inode)->i_orphan_idx = i * inodes_per_ob + j;
+			ext4_process_orphan(inode, &nr_truncates, &nr_orphans);
+		}
+	}
+
+	if (nr_orphans)
+		ext4_msg(sb, KERN_INFO, "%d orphan inode%s deleted",
+			 nr_orphans, str_plural(nr_orphans));
+	if (nr_truncates)
+		ext4_msg(sb, KERN_INFO, "%d truncate%s cleaned up",
+			 nr_truncates, str_plural(nr_truncates));
+#ifdef CONFIG_QUOTA
+	/* Turn off quotas if they were enabled for orphan cleanup */
+	if (quota_update) {
+		for (i = 0; i < EXT4_MAXQUOTAS; i++) {
+			if (sb_dqopt(sb)->files[i])
+				dquot_quota_off(sb, i);
+		}
+	}
+#endif
+	sb->s_flags = s_flags; /* Restore SB_RDONLY status */
+}
+
+void ext4_release_orphan_info(struct super_block *sb)
+{
+	int i;
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+
+	if (!oi->of_blocks)
+		return;
+	for (i = 0; i < oi->of_blocks; i++)
+		brelse(oi->of_binfo[i].ob_bh);
+	kvfree(oi->of_binfo);
+}
+
+static struct ext4_orphan_block_tail *ext4_orphan_block_tail(
+						struct super_block *sb,
+						struct buffer_head *bh)
+{
+	return (struct ext4_orphan_block_tail *)(bh->b_data + sb->s_blocksize -
+				sizeof(struct ext4_orphan_block_tail));
+}
+
+static int ext4_orphan_file_block_csum_verify(struct super_block *sb,
+					      struct buffer_head *bh)
+{
+	__u32 calculated;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+	struct ext4_orphan_block_tail *ot;
+	__le64 dsk_block_nr = cpu_to_le64(bh->b_blocknr);
+
+	if (!ext4_has_feature_metadata_csum(sb))
+		return 1;
+
+	ot = ext4_orphan_block_tail(sb, bh);
+	calculated = ext4_chksum(oi->of_csum_seed, (__u8 *)&dsk_block_nr,
+				 sizeof(dsk_block_nr));
+	calculated = ext4_chksum(calculated, (__u8 *)bh->b_data,
+				 inodes_per_ob * sizeof(__u32));
+	return le32_to_cpu(ot->ob_checksum) == calculated;
+}
+
+/* This gets called only when checksumming is enabled */
+void ext4_orphan_file_block_trigger(struct jbd2_buffer_trigger_type *triggers,
+				    struct buffer_head *bh,
+				    void *data, size_t size)
+{
+	struct super_block *sb = EXT4_TRIGGER(triggers)->sb;
+	__u32 csum;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+	struct ext4_orphan_block_tail *ot;
+	__le64 dsk_block_nr = cpu_to_le64(bh->b_blocknr);
+
+	csum = ext4_chksum(oi->of_csum_seed, (__u8 *)&dsk_block_nr,
+			   sizeof(dsk_block_nr));
+	csum = ext4_chksum(csum, (__u8 *)data, inodes_per_ob * sizeof(__u32));
+	ot = ext4_orphan_block_tail(sb, bh);
+	ot->ob_checksum = cpu_to_le32(csum);
+}
+
+int ext4_init_orphan_info(struct super_block *sb)
+{
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+	struct inode *inode;
+	int i, j;
+	int ret;
+	int free;
+	int loaded = 0;
+	__le32 *bdata;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
+	struct ext4_orphan_block_tail *ot;
+	ino_t orphan_ino = le32_to_cpu(EXT4_SB(sb)->s_es->s_orphan_file_inum);
+
+	if (!ext4_has_feature_orphan_file(sb))
+		return 0;
+
+	inode = ext4_iget(sb, orphan_ino, EXT4_IGET_SPECIAL);
+	if (IS_ERR(inode)) {
+		ext4_msg(sb, KERN_ERR, "get orphan inode failed");
+		return PTR_ERR(inode);
+	}
+	/*
+	 * This is just an artificial limit to prevent corrupted fs from
+	 * consuming absurd amounts of memory when pinning blocks of orphan
+	 * file in memory.
+	 */
+	if (inode->i_size > (EXT4_MAX_ORPHAN_FILE_BLOCKS << inode->i_blkbits)) {
+		ext4_msg(sb, KERN_ERR, "orphan file too big: %llu",
+			 (unsigned long long)inode->i_size);
+		ret = -EFSCORRUPTED;
+		goto out_put;
+	}
+	oi->of_blocks = inode->i_size >> sb->s_blocksize_bits;
+	oi->of_csum_seed = EXT4_I(inode)->i_csum_seed;
+	oi->of_binfo = kvmalloc_objs(struct ext4_orphan_block, oi->of_blocks);
+	if (!oi->of_binfo) {
+		ret = -ENOMEM;
+		goto out_put;
+	}
+	for (i = 0; i < oi->of_blocks; i++) {
+		oi->of_binfo[i].ob_bh = ext4_bread(NULL, inode, i, 0);
+		if (IS_ERR(oi->of_binfo[i].ob_bh)) {
+			ret = PTR_ERR(oi->of_binfo[i].ob_bh);
+			goto out_free;
+		}
+		if (!oi->of_binfo[i].ob_bh) {
+			ret = -EIO;
+			goto out_free;
+		}
+		loaded++;
+		ot = ext4_orphan_block_tail(sb, oi->of_binfo[i].ob_bh);
+		if (le32_to_cpu(ot->ob_magic) != EXT4_ORPHAN_BLOCK_MAGIC) {
+			ext4_error(sb, "orphan file block %d: bad magic", i);
+			ret = -EIO;
+			goto out_free;
+		}
+		if (!ext4_orphan_file_block_csum_verify(sb,
+						oi->of_binfo[i].ob_bh)) {
+			ext4_error(sb, "orphan file block %d: bad checksum", i);
+			ret = -EIO;
+			goto out_free;
+		}
+		bdata = (__le32 *)(oi->of_binfo[i].ob_bh->b_data);
+		free = 0;
+		for (j = 0; j < inodes_per_ob; j++)
+			if (bdata[j] == 0)
+				free++;
+		atomic_set(&oi->of_binfo[i].ob_free_entries, free);
+	}
+	iput(inode);
+	return 0;
+out_free:
+	while (loaded > 0) {
+		loaded--;
+		brelse(oi->of_binfo[loaded].ob_bh);
+	}
+	kvfree(oi->of_binfo);
+out_put:
+	iput(inode);
+	return ret;
+}
+
+int ext4_orphan_file_empty(struct super_block *sb)
+{
+	struct ext4_orphan_info *oi = &EXT4_SB(sb)->s_orphan_info;
+	int i;
+	int inodes_per_ob = ext4_inodes_per_orphan_block(sb);
+
+	if (!ext4_has_feature_orphan_file(sb))
+		return 1;
+	for (i = 0; i < oi->of_blocks; i++)
+		if (atomic_read(&oi->of_binfo[i].ob_free_entries) !=
+		    inodes_per_ob)
+			return 0;
+	return 1;
+}