[PATCH v7 1/2] block: fix signed int overflow in Amiga partition support

Michael Schmitz
2018-10-15T10:15:44Z

The Amiga partition parser module uses signed int for partition sector
address and count, which will overflow for disks larger than 1 TB.

Use sector_t as type for sector address and size to allow using disks
up to 2 TB without LBD support, and disks larger than 2 TB with LBD.

This bug was reported originally in 2012, and the fix was created by
the RDB author, Joanne Dow <jdow@earthlink.net>. A patch had been
discussed and reviewed on linux-m68k at that time but never officially
submitted. This patch differs from Joanne's patch only in its use of
sector_t instead of unsigned int. No checking for overflows is done
(see patch 2 of this series for that).

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=43511
Reported-by: Martin Steigerwald <Martin@lichtvoll.de>
Message-ID: <201206192146.09327.Martin@lichtvoll.de>
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Martin Steigerwald <Martin@lichtvoll.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

---

Changes from v3:

- split off change of sector address type as quick fix.
- cast to sector_t in sector address calculations.
- move overflow checking to separate patch for more thorough review.

Changes from v4:

Andreas Schwab:
- correct cast to sector_t in sector address calculations
---
block/partitions/amiga.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/block/partitions/amiga.c b/block/partitions/amiga.c
index 5609366..7ea9540 100644
--- a/block/partitions/amiga.c
+++ b/block/partitions/amiga.c
@@ -32,7 +32,8 @@ int amiga_partition(struct parsed_partitions *state)
unsigned char *data;
struct RigidDiskBlock *rdb;
struct PartitionBlock *pb;
- int start_sect, nr_sects, blk, part, res = 0;
+ sector_t start_sect, nr_sects;
+ int blk, part, res = 0;
int blksize = 1; /* Multiplier for disk block size */
int slot = 1;
char b[BDEVNAME_SIZE];
@@ -100,14 +101,14 @@ int amiga_partition(struct parsed_partitions *state)

/* Tell Kernel about it */

- nr_sects = (be32_to_cpu(pb->pb_Environment[10]) + 1 -
- be32_to_cpu(pb->pb_Environment[9])) *
+ nr_sects = ((sector_t) be32_to_cpu(pb->pb_Environment[10])
+ + 1 - be32_to_cpu(pb->pb_Environment[9])) *
be32_to_cpu(pb->pb_Environment[3]) *
be32_to_cpu(pb->pb_Environment[5]) *
blksize;
if (!nr_sects)
continue;
- start_sect = be32_to_cpu(pb->pb_Environment[9]) *
+ start_sect = (sector_t) be32_to_cpu(pb->pb_Environment[9]) *
be32_to_cpu(pb->pb_Environment[3]) *
be32_to_cpu(pb->pb_Environment[5]) *
blksize;
--
1.9.1