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From: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH][RESEND] mac: validate mac_partition is within sector
Date: Thu, 19 Nov 2015 17:18:54 -0800	[thread overview]
Message-ID: <20151120011854.GA12836@www.outflux.net> (raw)

If md->signature == MAC_DRIVER_MAGIC and md->block_size == 1023, a single
512 byte sector would be read (secsize / 512). However the partition
structure would be located past the end of the buffer (secsize % 512).

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
---
There doesn't seem to be a mac partition maintainer...
---
 block/partitions/mac.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/block/partitions/mac.c b/block/partitions/mac.c
index c2c48ec64b27..621317ac4d59 100644
--- a/block/partitions/mac.c
+++ b/block/partitions/mac.c
@@ -32,7 +32,7 @@ int mac_partition(struct parsed_partitions *state)
 	Sector sect;
 	unsigned char *data;
 	int slot, blocks_in_map;
-	unsigned secsize;
+	unsigned secsize, datasize, partoffset;
 #ifdef CONFIG_PPC_PMAC
 	int found_root = 0;
 	int found_root_goodness = 0;
@@ -50,10 +50,14 @@ int mac_partition(struct parsed_partitions *state)
 	}
 	secsize = be16_to_cpu(md->block_size);
 	put_dev_sector(sect);
-	data = read_part_sector(state, secsize/512, &sect);
+	datasize = round_down(secsize, 512);
+	data = read_part_sector(state, datasize / 512, &sect);
 	if (!data)
 		return -1;
-	part = (struct mac_partition *) (data + secsize%512);
+	partoffset = secsize % 512;
+	if (partoffset + sizeof(*part) > datasize)
+		return -1;
+	part = (struct mac_partition *) (data + partoffset);
 	if (be16_to_cpu(part->signature) != MAC_PARTITION_MAGIC) {
 		put_dev_sector(sect);
 		return 0;		/* not a MacOS disk */
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security

             reply	other threads:[~2015-11-20  1:19 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-20  1:18 Kees Cook [this message]
2015-11-20 21:31 ` [PATCH][RESEND] mac: validate mac_partition is within sector Jeff Moyer

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