udf: refactor inode_bmap() to handle error

Refactor inode_bmap() to handle error since udf_next_aext() can return
error now. On situations like ftruncate, udf_extend_file() can now
detect errors and bail out early without resorting to checking for
particular offsets and assuming internal behavior of these functions.

Reported-by: [e-mail]
Closes: https://syzkaller.appspot.com/bug?extid=7a4842f0b1801230a989
Tested-by: [e-mail]
Signed-off-by: Zhao Mengmeng <[e-mail]>
Suggested-by: Jan Kara <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

fs/udf/directory.c

···
 {
 	struct udf_inode_info *iinfo = UDF_I(dir);
 	int err = 0;
+	int8_t etype;
 
 	iter->dir = dir;
 	iter->bh[0] = iter->bh[1] = NULL;
···
 		goto out;
 	}
 
-	if (inode_bmap(dir, iter->pos >> dir->i_blkbits, &iter->epos,
-		       &iter->eloc, &iter->elen, &iter->loffset) !=
-	    (EXT_RECORDED_ALLOCATED >> 30)) {
+	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,
···
 	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;
···
 		udf_fiiter_update_elen(iter, old_elen);
 		return err;
 	}
-	if (inode_bmap(iter->dir, block, &iter->epos, &iter->eloc, &iter->elen,
-		       &iter->loffset) != (EXT_RECORDED_ALLOCATED >> 30)) {
+	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 %lu)\n",
 			(unsigned long long)block, iter->dir->i_ino);

fs/udf/inode.c

···
 
 static int udf_map_block(struct inode *inode, struct udf_map_rq *map)
 {
-	int err;
+	int ret;
 	struct udf_inode_info *iinfo = UDF_I(inode);
 
 	if (WARN_ON_ONCE(iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB))
···
 		uint32_t elen;
 		sector_t offset;
 		struct extent_position epos = {};
+		int8_t etype;
 
 		down_read(&iinfo->i_data_sem);
-		if (inode_bmap(inode, map->lblk, &epos, &eloc, &elen, &offset)
-				== (EXT_RECORDED_ALLOCATED >> 30)) {
+		ret = inode_bmap(inode, map->lblk, &epos, &eloc, &elen, &offset,
+				 &etype);
+		if (ret < 0)
+			goto out_read;
+		if (ret > 0 && etype == (EXT_RECORDED_ALLOCATED >> 30)) {
 			map->pblk = udf_get_lb_pblock(inode->i_sb, &eloc,
 							offset);
 			map->oflags |= UDF_BLK_MAPPED;
+			ret = 0;
 		}
+out_read:
 		up_read(&iinfo->i_data_sem);
 		brelse(epos.bh);
 
-		return 0;
+		return ret;
 	}
 
 	down_write(&iinfo->i_data_sem);
···
 	if (((loff_t)map->lblk) << inode->i_blkbits >= iinfo->i_lenExtents)
 		udf_discard_prealloc(inode);
 	udf_clear_extent_cache(inode);
-	err = inode_getblk(inode, map);
+	ret = inode_getblk(inode, map);
 	up_write(&iinfo->i_data_sem);
-	return err;
+	return ret;
 }
 
 static int __udf_get_block(struct inode *inode, sector_t block,
···
 	 */
 	udf_discard_prealloc(inode);
 
-	etype = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset);
-	within_last_ext = (etype != -1);
+	err = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset, &etype);
+	if (err < 0)
+		goto out;
+	within_last_ext = (err == 1);
 	/* We don't expect extents past EOF... */
 	WARN_ON_ONCE(within_last_ext &&
 		     elen > ((loff_t)offset + 1) << inode->i_blkbits);
···
 	return (elen >> 30);
 }
 
-int8_t inode_bmap(struct inode *inode, sector_t block,
-		  struct extent_position *pos, struct kernel_lb_addr *eloc,
-		  uint32_t *elen, sector_t *offset)
+/*
+ * Returns 1 on success, -errno on error, 0 on hit EOF.
+ */
+int inode_bmap(struct inode *inode, sector_t block, struct extent_position *pos,
+	       struct kernel_lb_addr *eloc, uint32_t *elen, sector_t *offset,
+	       int8_t *etype)
 {
 	unsigned char blocksize_bits = inode->i_sb->s_blocksize_bits;
 	loff_t lbcount = 0, bcount = (loff_t) block << blocksize_bits;
-	int8_t etype;
 	struct udf_inode_info *iinfo;
 	int err = 0;
 
···
 	}
 	*elen = 0;
 	do {
-		err = udf_next_aext(inode, pos, eloc, elen, &etype, 1);
+		err = udf_next_aext(inode, pos, eloc, elen, etype, 1);
 		if (err <= 0) {
 			if (err == 0) {
 				*offset = (bcount - lbcount) >> blocksize_bits;
 				iinfo->i_lenExtents = lbcount;
 			}
-			return -1;
+			return err;
 		}
 		lbcount += *elen;
 	} while (lbcount <= bcount);
···
 	udf_update_extent_cache(inode, lbcount - *elen, pos);
 	*offset = (bcount + *elen - lbcount) >> blocksize_bits;
 
-	return etype;
+	return 1;
 }

fs/udf/partition.c

···
 	sector_t ext_offset;
 	struct extent_position epos = {};
 	uint32_t phyblock;
+	int8_t etype;
+	int err = 0;
 
-	if (inode_bmap(inode, block, &epos, &eloc, &elen, &ext_offset) !=
-						(EXT_RECORDED_ALLOCATED >> 30))
+	err = inode_bmap(inode, block, &epos, &eloc, &elen, &ext_offset, &etype);
+	if (err <= 0 || etype != (EXT_RECORDED_ALLOCATED >> 30))
 		phyblock = 0xFFFFFFFF;
 	else {
 		map = &UDF_SB(sb)->s_partmaps[partition];

fs/udf/truncate.c

···
 	else
 		BUG();
 
-	etype = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset);
+	ret = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset, &etype);
+	if (ret < 0)
+		return ret;
 	byte_offset = (offset << sb->s_blocksize_bits) +
 		(inode->i_size & (sb->s_blocksize - 1));
-	if (etype == -1) {
+	if (ret == 0) {
 		/* We should extend the file? */
 		WARN_ON(byte_offset);
 		return 0;

fs/udf/udfdecl.h

···
 extern int udf_setsize(struct inode *, loff_t);
 extern void udf_evict_inode(struct inode *);
 extern int udf_write_inode(struct inode *, struct writeback_control *wbc);
-extern int8_t inode_bmap(struct inode *, sector_t, struct extent_position *,
-			 struct kernel_lb_addr *, uint32_t *, sector_t *);
+extern int inode_bmap(struct inode *inode, sector_t block,
+		      struct extent_position *pos, struct kernel_lb_addr *eloc,
+		      uint32_t *elen, sector_t *offset, int8_t *etype);
 int udf_get_block(struct inode *, sector_t, struct buffer_head *, int);
 extern int udf_setup_indirect_aext(struct inode *inode, udf_pblk_t block,
 				   struct extent_position *epos);