Re: [PATCH v8 1/2] block: fix signed int overflow in Amiga partition support

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On Tue, Jul 26, 2022 at 04:57:46PM +1200, Michael Schmitz wrote:
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@xxxxxxxxxxxxx>. 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@xxxxxxxxxxxx>
Message-ID: <201206192146.09327.Martin@xxxxxxxxxxxx>
Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Tested-by: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
 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 5c8624e26a54..f98191545d9a 100644
--- a/block/partitions/amiga.c
+++ b/block/partitions/amiga.c
@@ -31,7 +31,8 @@ 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;
 
@@ -96,14 +97,14 @@ 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])) *

Nit: we usually don't leave a whitespace afte a cast and the operators go
onto the previous line, i.e. this should be:

+		nr_sects = ((sector_t)be32_to_cpu(pb->pb_Environment[10]) + 1 -
+			    be32_to_cpu(pb->pb_Environment[9])) *

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>



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