[PATCH v3 7/9] cryptodisk: Fix incorrect calculation of start sector

[Patrick Steinhardt <ps@pks.im>]

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From: Glenn Washburn <development@efficientek.com>

Here dev is a grub_cryptodisk_t and dev->offset is offset in sectors of size
native to the cryptodisk device. The sector is correctly transformed into
native grub sector size, but then added to dev->offset which is not
transformed. It would be nice if the type system would help us with this.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Patrick Steinhardt <ps@pks.im>
---
 grub-core/disk/cryptodisk.c | 11 ++++-------
 include/grub/disk.h         |  7 +++++++
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index b2c6e9a7d..1eea4161f 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -757,9 +757,8 @@ grub_cryptodisk_read (grub_disk_t disk, grub_disk_addr_t sector,
 		size, sector, dev->offset);
 
   err = grub_disk_read (dev->source_disk,
-			(sector << (disk->log_sector_size
-				   - GRUB_DISK_SECTOR_BITS)) + dev->offset, 0,
-			size << disk->log_sector_size, buf);
+			grub_disk_from_native_sector (disk, sector + dev->offset),
+			0, size << disk->log_sector_size, buf);
   if (err)
     {
       grub_dprintf ("cryptodisk", "grub_disk_read failed with error %d\n", err);
@@ -816,12 +815,10 @@ grub_cryptodisk_write (grub_disk_t disk, grub_disk_addr_t sector,
     }
 
   /* Since ->write was called so disk.mod is loaded but be paranoid  */
-  
+  sector = sector + dev->offset;
   if (grub_disk_write_weak)
     err = grub_disk_write_weak (dev->source_disk,
-				(sector << (disk->log_sector_size
-					    - GRUB_DISK_SECTOR_BITS))
-				+ dev->offset,
+				grub_disk_from_native_sector (disk, sector),
 				0, size << disk->log_sector_size, tmp);
   else
     err = grub_error (GRUB_ERR_BUG, "disk.mod not loaded");
diff --git a/include/grub/disk.h b/include/grub/disk.h
index 316659fee..af9f886d3 100644
--- a/include/grub/disk.h
+++ b/include/grub/disk.h
@@ -174,6 +174,13 @@ typedef struct grub_disk_memberlist *grub_disk_memberlist_t;
 /* Return value of grub_disk_get_size() in case disk size is unknown. */
 #define GRUB_DISK_SIZE_UNKNOWN	 0xffffffffffffffffULL
 
+/* Convert to grub native disk sized sector from disk sized sector */
+static inline grub_disk_addr_t
+grub_disk_from_native_sector (grub_disk_t disk, grub_disk_addr_t sector)
+{
+  return sector << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS);
+}
+
 /* This is called from the memory manager.  */
 void grub_disk_cache_invalidate_all (void);
 
-- 
2.28.0


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