linux-kernel - Re: [PATCH] hfsplus: Refuse to mount volumes larger than 2TB

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Message-Id: <20091011005153.cc723dca.akpm@linux-foundation.org>
Date:	Sun, 11 Oct 2009 00:51:53 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	linux-kernel@...r.kernel.org, Eric Sesterhenn <snakebyte@....de>,
	Roman Zippel <zippel@...ux-m68k.org>, 550010@...s.debian.org
Subject: Re: [PATCH] hfsplus: Refuse to mount volumes larger than 2TB

On Sun, 11 Oct 2009 03:11:27 +0100 Ben Hutchings <ben@...adent.org.uk> wrote:

> As found in <http://bugs.debian.org/550010>, hfsplus is using type u32
> rather than sector_t for some sector number calculations.
> 
> In particular, hfsplus_get_block() does:
> 
>         u32 ablock, dblock, mask;
> ...
>         map_bh(bh_result, sb, (dblock << HFSPLUS_SB(sb).fs_shift) + HFSPLUS_SB(sb).blockoffset + (iblock & mask));
> 
> I am not confident that I can find and fix all cases where a sector
> number may be truncated.  For now, avoid data loss by refusing to mount
> HFS+ volumes with more than 2^32 sectors (2TB).
> 
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> Cc: stable@...nel.org
> ---
> --- a/fs/hfsplus/wrapper.c
> +++ b/fs/hfsplus/wrapper.c
> @@ -99,6 +99,10 @@
>  
>  	if (hfsplus_get_last_session(sb, &part_start, &part_size))
>  		return -EINVAL;
> +	if (part_start + part_size > 0x100000000) {
> +		pr_err("hfs: volumes larger than 2TB are not supported yet\n");
> +		return -EINVAL;
> +	}

part_start and part_size are sector_t.  This code will do weird overflow
things when sector_t is 32-bit.  Also 32-bit compilers will get upset at the
excessively large hex constant.

This should fix both issues:

--- a/fs/hfsplus/wrapper.c~hfsplus-refuse-to-mount-volumes-larger-than-2tb-fix
+++ a/fs/hfsplus/wrapper.c
@@ -99,7 +99,7 @@ int hfsplus_read_wrapper(struct super_bl
 
 	if (hfsplus_get_last_session(sb, &part_start, &part_size))
 		return -EINVAL;
-	if (part_start + part_size > 0x100000000) {
+	if ((u64)part_start + part_size > 0x100000000ULL) {
 		pr_err("hfs: volumes larger than 2TB are not supported yet\n");
 		return -EINVAL;
 	}
_

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