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

Andrew Morton
2009-10-11T07:53:13Z

On Sun, 11 Oct 2009 03:11:27 +0100 Ben Hutchings <ben@decadent.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@decadent.org.uk>
> Cc: stable@kernel.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;
}
_