Re: [PATCH v2] f2fs: avoid out-of-range memory access

Chao Yu
2019-07-03T02:07:14Z

Hi Ocean,

If filesystem is corrupted, it should fail mount due to below check in
f2fs_sanity_check_ckpt(), so we are safe in read_compacted_summaries() to access
entries[0,blk_off], right?

for (i = 0; i < NR_CURSEG_DATA_TYPE; i++) {
if (le32_to_cpu(ckpt->cur_data_segno[i]) >= main_segs ||
le16_to_cpu(ckpt->cur_data_blkoff[i]) >= blocks_per_seg)
return 1;

Thanks,

On 2019/7/2 16:05, Ocean Chen wrote:
> blk_off might over 512 due to fs corrupt.
> Use ENTRIES_IN_SUM to protect invalid memory access.
>
> v2:
> - fix typo
> Signed-off-by: Ocean Chen <oceanchen@google.com>
> ---
> fs/f2fs/segment.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 8dee063c833f..a5e8af0bd62e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3403,6 +3403,8 @@ static int read_compacted_summaries(struct f2fs_sb_info *sbi)
>
> for (j = 0; j < blk_off; j++) {
> struct f2fs_summary *s;
> + if (j >= ENTRIES_IN_SUM)
> + return -EFAULT;
> s = (struct f2fs_summary *)(kaddr + offset);
> seg_i->sum_blk->entries[j] = *s;
> offset += SUMMARY_SIZE;
>