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disk: Move hardcoded max disk size literal to a GRUB_DISK_MAX_SECTORS in disk.h

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There is a hardcoded maximum disk size that can be read or written from,
currently set at 1 EiB in grub_disk_adjust_range(). Move the literal into a
macro in disk.h, so our assumptions are more visible. This hard coded limit
does not prevent using larger disks, just GRUB won't read/write past the
limit. The comment accompanying this restriction didn't quite make sense to
me, so its been modified too.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Glenn Washburn 2020-11-30 23:16:19 -06:00 committed by Daniel Kiper
parent 8919eecd84
commit 407ddead69
2 changed files with 14 additions and 7 deletions
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15
grub-core/kern/disk_common.c
View File

@ -32,13 +32,14 @@ grub_disk_adjust_range (grub_disk_t disk, grub_disk_addr_t *sector,
/* Transform total_sectors to number of 512B blocks. */
total_sectors = disk->total_sectors << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS);
/* Some drivers have problems with disks above reasonable.
Treat unknown as 1EiB disk. While on it, clamp the size to 1EiB.
Just one condition is enough since GRUB_DISK_UNKNOWN_SIZE << ls is always
above 9EiB.
*/
if (total_sectors > (1ULL << 51))
total_sectors = (1ULL << 51);
/*
* Some drivers have problems with disks above reasonable sizes.
* Clamp the size to GRUB_DISK_MAX_SECTORS. Just one condition is enough
* since GRUB_DISK_SIZE_UNKNOWN is always above GRUB_DISK_MAX_SECTORS,
* assuming a maximum 4 KiB sector size.
*/
if (total_sectors > GRUB_DISK_MAX_SECTORS)
total_sectors = GRUB_DISK_MAX_SECTORS;
if ((total_sectors <= *sector
|| ((*offset + size + GRUB_DISK_SECTOR_SIZE - 1)

6
include/grub/disk.h
View File

@ -161,6 +161,12 @@ typedef struct grub_disk_memberlist *grub_disk_memberlist_t;
#define GRUB_DISK_SECTOR_SIZE 0x200
#define GRUB_DISK_SECTOR_BITS 9
/*
* Some drivers have problems with disks above reasonable sizes.
* Set max disk size at 1 EiB.
*/
#define GRUB_DISK_MAX_SECTORS (1ULL << (60 - GRUB_DISK_SECTOR_BITS))
/* The maximum number of disk caches. */
#define GRUB_DISK_CACHE_NUM 1021