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: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx> Cc: linux-scsi@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/scsi/sd_zbc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c index 26af5ab7d7c1..2c377e4cdb2b 100644 --- a/drivers/scsi/sd_zbc.c +++ b/drivers/scsi/sd_zbc.c @@ -295,7 +295,7 @@ int sd_zbc_report_zones(struct gendisk *disk, sector_t sector, (lba < start_lba || lba >= start_lba + zone_length)) || (zone_idx > 0 && start_lba != lba) || - start_lba + zone_length < start_lba) { + add_would_overflow(start_lba, zone_length)) { sd_printk(KERN_ERR, sdkp, "Zone %d at LBA %llu is invalid: %llu + %llu\n", zone_idx, lba, start_lba, zone_length); -- 2.34.1
