udf: Refactor intentional wrap-around test In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Jan Kara <jack@suse.com> Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c index ab3ffc3..5c88300c 100644 --- a/fs/udf/balloc.c +++ b/fs/udf/balloc.c
@@ -139,7 +139,7 @@ static void udf_bitmap_free_blocks(struct super_block *sb, mutex_lock(&sbi->s_alloc_mutex); partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; - if (bloc->logicalBlockNum + count < count || + if (add_would_overflow(count, bloc->logicalBlockNum) || (bloc->logicalBlockNum + count) > partmap->s_partition_len) { udf_debug("%u < %d || %u + %u > %u\n", bloc->logicalBlockNum, 0, @@ -390,7 +390,7 @@ static void udf_table_free_blocks(struct super_block *sb, mutex_lock(&sbi->s_alloc_mutex); partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; - if (bloc->logicalBlockNum + count < count || + if (add_would_overflow(count, bloc->logicalBlockNum) || (bloc->logicalBlockNum + count) > partmap->s_partition_len) { udf_debug("%u < %d || %u + %u > %u\n", bloc->logicalBlockNum, 0,