On Mon, Jan 14, 2013 at 07:37:12PM -0500, Theodore Ts'o wrote:
> If the user attemps to create a 512MB cluster, we need to adjust the
> defaults to avoid a 32-bit overflow of s_blocks_per_group. Also check
> to make sure that the caller of ext2fs_initialize() has not given a
> value of s_clusters_per_group that would result in an overflow of
> s_blocks_per_group.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
The patch itself looks good to me. Feel free to add:
Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
FWIW, I wonder why we need to add such complex logical to handle a
corner case. I guess no one wants to use a 512MB cluster. So changing
max cluster size from 512MB to 256MB is very simple and straightfoward.
Regards,
- Zheng
> ---
> lib/ext2fs/initialize.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
> index b0c15d2..5afdc27 100644
> --- a/lib/ext2fs/initialize.c
> +++ b/lib/ext2fs/initialize.c
> @@ -207,6 +207,8 @@ errcode_t ext2fs_initialize(const char *name, int flags,
> super->s_log_block_size;
>
> if (bigalloc_flag) {
> + unsigned long long bpg;
> +
> if (param->s_blocks_per_group &&
> param->s_clusters_per_group &&
> ((param->s_clusters_per_group * EXT2FS_CLUSTER_RATIO(fs)) !=
> @@ -220,12 +222,19 @@ errcode_t ext2fs_initialize(const char *name, int flags,
> super->s_clusters_per_group =
> param->s_blocks_per_group /
> EXT2FS_CLUSTER_RATIO(fs);
> - else
> + else if (super->s_log_cluster_size + 15 < 32)
> super->s_clusters_per_group = fs->blocksize * 8;
> + else
> + super->s_clusters_per_group = (fs->blocksize - 1) * 8;
> if (super->s_clusters_per_group > EXT2_MAX_CLUSTERS_PER_GROUP(super))
> super->s_clusters_per_group = EXT2_MAX_CLUSTERS_PER_GROUP(super);
> - super->s_blocks_per_group = EXT2FS_C2B(fs,
> - super->s_clusters_per_group);
> + bpg = EXT2FS_C2B(fs,
> + (unsigned long long) super->s_clusters_per_group);
> + if (bpg >= (((unsigned long long) 1) << 32)) {
> + retval = EXT2_ET_INVALID_ARGUMENT;
> + goto cleanup;
> + }
> + super->s_blocks_per_group = bpg;
> } else {
> set_field(s_blocks_per_group, fs->blocksize * 8);
> if (super->s_blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(super))
> --
> 1.7.12.rc0.22.gcdd159b
>
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