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, 543 insertions, 0 deletions

diff --git a/fs/udf/directory.c b/fs/udf/directory.c
new file mode 100644
index 000000000..6b4ac7464
--- /dev/null
+++ b/fs/udf/directory.c
@@ -0,0 +1,543 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * directory.c
+ *
+ * PURPOSE
+ *	Directory related functions
+ *
+ */
+
+#include "udfdecl.h"
+#include "udf_i.h"
+
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/bio.h>
+#include <linux/crc-itu-t.h>
+#include <linux/iversion.h>
+
+static int udf_verify_fi(struct udf_fileident_iter *iter)
+{
+	unsigned int len;
+
+	if (iter->fi.descTag.tagIdent != cpu_to_le16(TAG_IDENT_FID)) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has entry at pos %llu with incorrect tag %x\n",
+			iter->dir->i_ino, (unsigned long long)iter->pos,
+			le16_to_cpu(iter->fi.descTag.tagIdent));
+		return -EFSCORRUPTED;
+	}
+	len = udf_dir_entry_len(&iter->fi);
+	if (le16_to_cpu(iter->fi.lengthOfImpUse) & 3) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has entry at pos %llu with unaligned length of impUse field\n",
+			iter->dir->i_ino, (unsigned long long)iter->pos);
+		return -EFSCORRUPTED;
+	}
+	/*
+	 * This is in fact allowed by the spec due to long impUse field but
+	 * we don't support it. If there is real media with this large impUse
+	 * field, support can be added.
+	 */
+	if (len > 1 << iter->dir->i_blkbits) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has too big (%u) entry at pos %llu\n",
+			iter->dir->i_ino, len, (unsigned long long)iter->pos);
+		return -EFSCORRUPTED;
+	}
+	if (iter->pos + len > iter->dir->i_size) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has entry past directory size at pos %llu\n",
+			iter->dir->i_ino, (unsigned long long)iter->pos);
+		return -EFSCORRUPTED;
+	}
+	if (udf_dir_entry_len(&iter->fi) !=
+	    sizeof(struct tag) + le16_to_cpu(iter->fi.descTag.descCRCLength)) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has entry where CRC length (%u) does not match entry length (%u)\n",
+			iter->dir->i_ino,
+			(unsigned)le16_to_cpu(iter->fi.descTag.descCRCLength),
+			(unsigned)(udf_dir_entry_len(&iter->fi) -
+							sizeof(struct tag)));
+		return -EFSCORRUPTED;
+	}
+	return 0;
+}
+
+static int udf_copy_fi(struct udf_fileident_iter *iter)
+{
+	struct udf_inode_info *iinfo = UDF_I(iter->dir);
+	u32 blksize = 1 << iter->dir->i_blkbits;
+	u32 off, len, nameoff;
+	int err;
+
+	/* Skip copying when we are at EOF */
+	if (iter->pos >= iter->dir->i_size) {
+		iter->name = NULL;
+		return 0;
+	}
+	if (iter->dir->i_size < iter->pos + sizeof(struct fileIdentDesc)) {
+		udf_err(iter->dir->i_sb,
+			"directory (ino %llu) has entry straddling EOF\n",
+			iter->dir->i_ino);
+		return -EFSCORRUPTED;
+	}
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		memcpy(&iter->fi, iinfo->i_data + iinfo->i_lenEAttr + iter->pos,
+		       sizeof(struct fileIdentDesc));
+		err = udf_verify_fi(iter);
+		if (err < 0)
+			return err;
+		iter->name = iinfo->i_data + iinfo->i_lenEAttr + iter->pos +
+			sizeof(struct fileIdentDesc) +
+			le16_to_cpu(iter->fi.lengthOfImpUse);
+		return 0;
+	}
+
+	off = iter->pos & (blksize - 1);
+	len = min_t(u32, sizeof(struct fileIdentDesc), blksize - off);
+	memcpy(&iter->fi, iter->bh[0]->b_data + off, len);
+	if (len < sizeof(struct fileIdentDesc))
+		memcpy((char *)(&iter->fi) + len, iter->bh[1]->b_data,
+		       sizeof(struct fileIdentDesc) - len);
+	err = udf_verify_fi(iter);
+	if (err < 0)
+		return err;
+
+	/* Handle directory entry name */
+	nameoff = off + sizeof(struct fileIdentDesc) +
+				le16_to_cpu(iter->fi.lengthOfImpUse);
+	if (off + udf_dir_entry_len(&iter->fi) <= blksize) {
+		iter->name = iter->bh[0]->b_data + nameoff;
+	} else if (nameoff >= blksize) {
+		iter->name = iter->bh[1]->b_data + (nameoff - blksize);
+	} else {
+		iter->name = iter->namebuf;
+		len = blksize - nameoff;
+		memcpy(iter->name, iter->bh[0]->b_data + nameoff, len);
+		memcpy(iter->name + len, iter->bh[1]->b_data,
+		       iter->fi.lengthFileIdent - len);
+	}
+	return 0;
+}
+
+/* Readahead 8k once we are at 8k boundary */
+static void udf_readahead_dir(struct udf_fileident_iter *iter)
+{
+	unsigned int ralen = 16 >> (iter->dir->i_blkbits - 9);
+	struct buffer_head *tmp, *bha[16];
+	int i, num;
+	udf_pblk_t blk;
+
+	if (iter->loffset & (ralen - 1))
+		return;
+
+	if (iter->loffset + ralen > (iter->elen >> iter->dir->i_blkbits))
+		ralen = (iter->elen >> iter->dir->i_blkbits) - iter->loffset;
+	num = 0;
+	for (i = 0; i < ralen; i++) {
+		blk = udf_get_lb_pblock(iter->dir->i_sb, &iter->eloc,
+					iter->loffset + i);
+		tmp = sb_getblk(iter->dir->i_sb, blk);
+		if (tmp && !buffer_uptodate(tmp) && !buffer_locked(tmp))
+			bha[num++] = tmp;
+		else
+			brelse(tmp);
+	}
+	if (num) {
+		bh_readahead_batch(num, bha, REQ_RAHEAD);
+		for (i = 0; i < num; i++)
+			brelse(bha[i]);
+	}
+}
+
+static struct buffer_head *udf_fiiter_bread_blk(struct udf_fileident_iter *iter)
+{
+	udf_pblk_t blk;
+
+	udf_readahead_dir(iter);
+	blk = udf_get_lb_pblock(iter->dir->i_sb, &iter->eloc, iter->loffset);
+	return sb_bread(iter->dir->i_sb, blk);
+}
+
+/*
+ * Updates loffset to point to next directory block; eloc, elen & epos are
+ * updated if we need to traverse to the next extent as well.
+ */
+static int udf_fiiter_advance_blk(struct udf_fileident_iter *iter)
+{
+	int8_t etype = -1;
+	int err = 0;
+
+	iter->loffset++;
+	if (iter->loffset < DIV_ROUND_UP(iter->elen, 1<<iter->dir->i_blkbits))
+		return 0;
+
+	iter->loffset = 0;
+	err = udf_next_aext(iter->dir, &iter->epos, &iter->eloc,
+			    &iter->elen, &etype, 1);
+	if (err < 0)
+		return err;
+	else if (err == 0 || etype != (EXT_RECORDED_ALLOCATED >> 30)) {
+		if (iter->pos == iter->dir->i_size) {
+			iter->elen = 0;
+			return 0;
+		}
+		udf_err(iter->dir->i_sb,
+			"extent after position %llu not allocated in directory (ino %llu)\n",
+			(unsigned long long)iter->pos, iter->dir->i_ino);
+		return -EFSCORRUPTED;
+	}
+	return 0;
+}
+
+static int udf_fiiter_load_bhs(struct udf_fileident_iter *iter)
+{
+	int blksize = 1 << iter->dir->i_blkbits;
+	int off = iter->pos & (blksize - 1);
+	int err;
+	struct fileIdentDesc *fi;
+
+	/* Is there any further extent we can map from? */
+	if (!iter->bh[0] && iter->elen) {
+		iter->bh[0] = udf_fiiter_bread_blk(iter);
+		if (!iter->bh[0]) {
+			err = -ENOMEM;
+			goto out_brelse;
+		}
+		if (!buffer_uptodate(iter->bh[0])) {
+			err = -EIO;
+			goto out_brelse;
+		}
+	}
+	/* There's no next block so we are done */
+	if (iter->pos >= iter->dir->i_size)
+		return 0;
+	/* Need to fetch next block as well? */
+	if (off + sizeof(struct fileIdentDesc) > blksize)
+		goto fetch_next;
+	fi = (struct fileIdentDesc *)(iter->bh[0]->b_data + off);
+	/* Need to fetch next block to get name? */
+	if (off + udf_dir_entry_len(fi) > blksize) {
+fetch_next:
+		err = udf_fiiter_advance_blk(iter);
+		if (err)
+			goto out_brelse;
+		iter->bh[1] = udf_fiiter_bread_blk(iter);
+		if (!iter->bh[1]) {
+			err = -ENOMEM;
+			goto out_brelse;
+		}
+		if (!buffer_uptodate(iter->bh[1])) {
+			err = -EIO;
+			goto out_brelse;
+		}
+	}
+	return 0;
+out_brelse:
+	brelse(iter->bh[0]);
+	brelse(iter->bh[1]);
+	iter->bh[0] = iter->bh[1] = NULL;
+	return err;
+}
+
+int udf_fiiter_init(struct udf_fileident_iter *iter, struct inode *dir,
+		    loff_t pos)
+{
+	struct udf_inode_info *iinfo = UDF_I(dir);
+	int err = 0;
+	int8_t etype;
+
+	iter->dir = dir;
+	iter->bh[0] = iter->bh[1] = NULL;
+	iter->pos = pos;
+	iter->elen = 0;
+	iter->epos.bh = NULL;
+	iter->name = NULL;
+	/*
+	 * When directory is verified, we don't expect directory iteration to
+	 * fail and it can be difficult to undo without corrupting filesystem.
+	 * So just do not allow memory allocation failures here.
+	 */
+	iter->namebuf = kmalloc(UDF_NAME_LEN_CS0, GFP_KERNEL | __GFP_NOFAIL);
+
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		err = udf_copy_fi(iter);
+		goto out;
+	}
+
+	err = inode_bmap(dir, iter->pos >> dir->i_blkbits, &iter->epos,
+			 &iter->eloc, &iter->elen, &iter->loffset, &etype);
+	if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30)) {
+		if (pos == dir->i_size)
+			return 0;
+		udf_err(dir->i_sb,
+			"position %llu not allocated in directory (ino %llu)\n",
+			(unsigned long long)pos, dir->i_ino);
+		err = -EFSCORRUPTED;
+		goto out;
+	}
+	err = udf_fiiter_load_bhs(iter);
+	if (err < 0)
+		goto out;
+	err = udf_copy_fi(iter);
+out:
+	if (err < 0)
+		udf_fiiter_release(iter);
+	return err;
+}
+
+int udf_fiiter_advance(struct udf_fileident_iter *iter)
+{
+	unsigned int oldoff, len;
+	int blksize = 1 << iter->dir->i_blkbits;
+	int err;
+
+	oldoff = iter->pos & (blksize - 1);
+	len = udf_dir_entry_len(&iter->fi);
+	iter->pos += len;
+	if (UDF_I(iter->dir)->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
+		if (oldoff + len >= blksize) {
+			brelse(iter->bh[0]);
+			iter->bh[0] = NULL;
+			/* Next block already loaded? */
+			if (iter->bh[1]) {
+				iter->bh[0] = iter->bh[1];
+				iter->bh[1] = NULL;
+			} else {
+				err = udf_fiiter_advance_blk(iter);
+				if (err < 0)
+					return err;
+			}
+		}
+		err = udf_fiiter_load_bhs(iter);
+		if (err < 0)
+			return err;
+	}
+	return udf_copy_fi(iter);
+}
+
+void udf_fiiter_release(struct udf_fileident_iter *iter)
+{
+	iter->dir = NULL;
+	brelse(iter->bh[0]);
+	brelse(iter->bh[1]);
+	iter->bh[0] = iter->bh[1] = NULL;
+	kfree(iter->namebuf);
+	iter->namebuf = NULL;
+}
+
+static void udf_copy_to_bufs(void *buf1, int len1, void *buf2, int len2,
+			     int off, void *src, int len)
+{
+	int copy;
+
+	if (off >= len1) {
+		off -= len1;
+	} else {
+		copy = min(off + len, len1) - off;
+		memcpy(buf1 + off, src, copy);
+		src += copy;
+		len -= copy;
+		off = 0;
+	}
+	if (len > 0) {
+		if (WARN_ON_ONCE(off + len > len2 || !buf2))
+			return;
+		memcpy(buf2 + off, src, len);
+	}
+}
+
+static uint16_t udf_crc_fi_bufs(void *buf1, int len1, void *buf2, int len2,
+				int off, int len)
+{
+	int copy;
+	uint16_t crc = 0;
+
+	if (off >= len1) {
+		off -= len1;
+	} else {
+		copy = min(off + len, len1) - off;
+		crc = crc_itu_t(crc, buf1 + off, copy);
+		len -= copy;
+		off = 0;
+	}
+	if (len > 0) {
+		if (WARN_ON_ONCE(off + len > len2 || !buf2))
+			return 0;
+		crc = crc_itu_t(crc, buf2 + off, len);
+	}
+	return crc;
+}
+
+static void udf_copy_fi_to_bufs(char *buf1, int len1, char *buf2, int len2,
+				int off, struct fileIdentDesc *fi,
+				uint8_t *impuse, uint8_t *name)
+{
+	uint16_t crc;
+	int fioff = off;
+	int crcoff = off + sizeof(struct tag);
+	unsigned int crclen = udf_dir_entry_len(fi) - sizeof(struct tag);
+	char zeros[UDF_NAME_PAD] = {};
+	int endoff = off + udf_dir_entry_len(fi);
+
+	udf_copy_to_bufs(buf1, len1, buf2, len2, off, fi,
+			 sizeof(struct fileIdentDesc));
+	off += sizeof(struct fileIdentDesc);
+	if (impuse)
+		udf_copy_to_bufs(buf1, len1, buf2, len2, off, impuse,
+				 le16_to_cpu(fi->lengthOfImpUse));
+	off += le16_to_cpu(fi->lengthOfImpUse);
+	if (name) {
+		udf_copy_to_bufs(buf1, len1, buf2, len2, off, name,
+				 fi->lengthFileIdent);
+		off += fi->lengthFileIdent;
+		udf_copy_to_bufs(buf1, len1, buf2, len2, off, zeros,
+				 endoff - off);
+	}
+
+	crc = udf_crc_fi_bufs(buf1, len1, buf2, len2, crcoff, crclen);
+	fi->descTag.descCRC = cpu_to_le16(crc);
+	fi->descTag.descCRCLength = cpu_to_le16(crclen);
+	fi->descTag.tagChecksum = udf_tag_checksum(&fi->descTag);
+
+	udf_copy_to_bufs(buf1, len1, buf2, len2, fioff, fi, sizeof(struct tag));
+}
+
+void udf_fiiter_write_fi(struct udf_fileident_iter *iter, uint8_t *impuse)
+{
+	struct udf_inode_info *iinfo = UDF_I(iter->dir);
+	void *buf1, *buf2 = NULL;
+	int len1, len2 = 0, off;
+	int blksize = 1 << iter->dir->i_blkbits;
+
+	off = iter->pos & (blksize - 1);
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		buf1 = iinfo->i_data + iinfo->i_lenEAttr;
+		len1 = iter->dir->i_size;
+	} else {
+		buf1 = iter->bh[0]->b_data;
+		len1 = blksize;
+		if (iter->bh[1]) {
+			buf2 = iter->bh[1]->b_data;
+			len2 = blksize;
+		}
+	}
+
+	udf_copy_fi_to_bufs(buf1, len1, buf2, len2, off, &iter->fi, impuse,
+			    iter->name == iter->namebuf ? iter->name : NULL);
+
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		mark_inode_dirty(iter->dir);
+	} else {
+		mmb_mark_buffer_dirty(iter->bh[0], &iinfo->i_metadata_bhs);
+		if (iter->bh[1])
+			mmb_mark_buffer_dirty(iter->bh[1],
+					      &iinfo->i_metadata_bhs);
+	}
+	inode_inc_iversion(iter->dir);
+}
+
+void udf_fiiter_update_elen(struct udf_fileident_iter *iter, uint32_t new_elen)
+{
+	struct udf_inode_info *iinfo = UDF_I(iter->dir);
+	int diff = new_elen - iter->elen;
+
+	/* Skip update when we already went past the last extent */
+	if (!iter->elen)
+		return;
+	iter->elen = new_elen;
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_SHORT)
+		iter->epos.offset -= sizeof(struct short_ad);
+	else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)
+		iter->epos.offset -= sizeof(struct long_ad);
+	udf_write_aext(iter->dir, &iter->epos, &iter->eloc, iter->elen, 1);
+	iinfo->i_lenExtents += diff;
+	mark_inode_dirty(iter->dir);
+}
+
+/* Append new block to directory. @iter is expected to point at EOF */
+int udf_fiiter_append_blk(struct udf_fileident_iter *iter)
+{
+	struct udf_inode_info *iinfo = UDF_I(iter->dir);
+	int blksize = 1 << iter->dir->i_blkbits;
+	struct buffer_head *bh;
+	sector_t block;
+	uint32_t old_elen = iter->elen;
+	int err;
+	int8_t etype;
+
+	if (WARN_ON_ONCE(iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB))
+		return -EINVAL;
+
+	/* Round up last extent in the file */
+	udf_fiiter_update_elen(iter, ALIGN(iter->elen, blksize));
+
+	/* Allocate new block and refresh mapping information */
+	block = iinfo->i_lenExtents >> iter->dir->i_blkbits;
+	bh = udf_bread(iter->dir, block, 1, &err);
+	if (!bh) {
+		udf_fiiter_update_elen(iter, old_elen);
+		return err;
+	}
+	err = inode_bmap(iter->dir, block, &iter->epos, &iter->eloc, &iter->elen,
+		   &iter->loffset, &etype);
+	if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30)) {
+		udf_err(iter->dir->i_sb,
+			"block %llu not allocated in directory (ino %llu)\n",
+			(unsigned long long)block, iter->dir->i_ino);
+		return -EFSCORRUPTED;
+	}
+	if (!(iter->pos & (blksize - 1))) {
+		brelse(iter->bh[0]);
+		iter->bh[0] = bh;
+	} else {
+		iter->bh[1] = bh;
+	}
+	return 0;
+}
+
+struct short_ad *udf_get_fileshortad(uint8_t *ptr, int maxoffset, uint32_t *offset,
+			      int inc)
+{
+	struct short_ad *sa;
+
+	if ((!ptr) || (!offset)) {
+		pr_err("%s: invalidparms\n", __func__);
+		return NULL;
+	}
+
+	if ((*offset + sizeof(struct short_ad)) > maxoffset)
+		return NULL;
+	else {
+		sa = (struct short_ad *)ptr;
+		if (sa->extLength == 0)
+			return NULL;
+	}
+
+	if (inc)
+		*offset += sizeof(struct short_ad);
+	return sa;
+}
+
+struct long_ad *udf_get_filelongad(uint8_t *ptr, int maxoffset, uint32_t *offset, int inc)
+{
+	struct long_ad *la;
+
+	if ((!ptr) || (!offset)) {
+		pr_err("%s: invalidparms\n", __func__);
+		return NULL;
+	}
+
+	if ((*offset + sizeof(struct long_ad)) > maxoffset)
+		return NULL;
+	else {
+		la = (struct long_ad *)ptr;
+		if (la->extLength == 0)
+			return NULL;
+	}
+
+	if (inc)
+		*offset += sizeof(struct long_ad);
+	return la;
+}