Messages in this thread | | | Date | Mon, 8 Jul 2019 11:21:11 +0800 | From | Ocean Chen <> | Subject | Re: [PATCH v2] f2fs: avoid out-of-range memory access |
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Hi YuChao,
Yes, we got externel researcher reports this security vulnerability.
And dump info is better when blk_off is invalid. I'll prepare the next patch for it.
On Thu, Jul 04, 2019 at 03:11:27PM +0800, Chao Yu wrote: > Hi Ocean, > > On 2019/7/3 23:03, Ocean Chen wrote: > > Hi Yu Chao, > > > > The cur_data_segno only was checked in mount process. In terms of > > security concern, it's better to check value before using it. I know the > > Could you explain more about security concern.. Do you get any report from user > or tools that complaining f2fs issue/codes? > > I'm not against sanity check for basic core data of filesystem in run-time, but, > in order to troubleshoot root cause of this issue we can trigger panic directly > to dump more info under F2FS_CHECK_FS macro. > > So, maybe we can change as below? > > blk_off = le16_to_cpu(ckpt->cur_data_blkoff[i]); > +if (blk_off > ENTRIES_IN_SUM) { > + f2fs_bug_on(1); > + f2fs_put_page(page, 1); > + return -EFAULT; > +} > > Thanks, > > > risk is low. IMHO, it can be safer. > > BTW, I found we can only check blk_off before for loop instead of > > checking 'j' in each iteratoin. > > > > On Wed, Jul 03, 2019 at 10:07:11AM +0800, Chao Yu wrote: > >> 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; > >>> > > . > >
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