[PATCH AUTOSEL 4.19 2/4] udf: prevent integer overflow in udf_bitmap_free_blocks()

[Sasha Levin]

From: Roman Smirnov <r.smirnov@xxxxxx>

[ Upstream commit 56e69e59751d20993f243fb7dd6991c4e522424c ]

An overflow may occur if the function is called with the last
block and an offset greater than zero. It is necessary to add
a check to avoid this.

Found by Linux Verification Center (linuxtesting.org) with Svace.

[JK: Make test cover also unalloc table freeing]

Link: https://patch.msgid.link/20240620072413.7448-1-r.smirnov@xxxxxx
Suggested-by: Jan Kara <jack@xxxxxxxx>
Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/udf/balloc.c | 36 +++++++++++++-----------------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index 0dc98bbad9c46..ac45f25bf40cc 100644
--- a/fs/udf/balloc.c
+++ b/fs/udf/balloc.c
@@ -22,6 +22,7 @@
 #include "udfdecl.h"
 
 #include <linux/bitops.h>
+#include <linux/overflow.h>
 
 #include "udf_i.h"
 #include "udf_sb.h"
@@ -133,7 +134,6 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
 {
 	struct udf_sb_info *sbi = UDF_SB(sb);
 	struct buffer_head *bh = NULL;
-	struct udf_part_map *partmap;
 	unsigned long block;
 	unsigned long block_group;
 	unsigned long bit;
@@ -142,19 +142,9 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
 	unsigned long overflow;
 
 	mutex_lock(&sbi->s_alloc_mutex);
-	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum + count < count ||
-	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
-		udf_debug("%u < %d || %u + %u > %u\n",
-			  bloc->logicalBlockNum, 0,
-			  bloc->logicalBlockNum, count,
-			  partmap->s_partition_len);
-		goto error_return;
-	}
-
+	/* We make sure this cannot overflow when mounting the filesystem */
 	block = bloc->logicalBlockNum + offset +
 		(sizeof(struct spaceBitmapDesc) << 3);
-
 	do {
 		overflow = 0;
 		block_group = block >> (sb->s_blocksize_bits + 3);
@@ -375,7 +365,6 @@ static void udf_table_free_blocks(struct super_block *sb,
 				  uint32_t count)
 {
 	struct udf_sb_info *sbi = UDF_SB(sb);
-	struct udf_part_map *partmap;
 	uint32_t start, end;
 	uint32_t elen;
 	struct kernel_lb_addr eloc;
@@ -384,16 +373,6 @@ static void udf_table_free_blocks(struct super_block *sb,
 	struct udf_inode_info *iinfo;
 
 	mutex_lock(&sbi->s_alloc_mutex);
-	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum + count < count ||
-	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
-		udf_debug("%u < %d || %u + %u > %u\n",
-			  bloc->logicalBlockNum, 0,
-			  bloc->logicalBlockNum, count,
-			  partmap->s_partition_len);
-		goto error_return;
-	}
-
 	iinfo = UDF_I(table);
 	udf_add_free_space(sb, sbi->s_partition, count);
 
@@ -668,6 +647,17 @@ void udf_free_blocks(struct super_block *sb, struct inode *inode,
 {
 	uint16_t partition = bloc->partitionReferenceNum;
 	struct udf_part_map *map = &UDF_SB(sb)->s_partmaps[partition];
+	uint32_t blk;
+
+	if (check_add_overflow(bloc->logicalBlockNum, offset, &blk) ||
+	    check_add_overflow(blk, count, &blk) ||
+	    bloc->logicalBlockNum + count > map->s_partition_len) {
+		udf_debug("Invalid request to free blocks: (%d, %u), off %u, "
+			  "len %u, partition len %u\n",
+			  partition, bloc->logicalBlockNum, offset, count,
+			  map->s_partition_len);
+		return;
+	}
 
 	if (map->s_partition_flags & UDF_PART_FLAG_UNALLOC_BITMAP) {
 		udf_bitmap_free_blocks(sb, map->s_uspace.s_bitmap,
-- 
2.43.0