On Tue, 20 Aug 2024 23:00:05 -0400, Kent Overstreet wrote: > > When the nr value of a signle entry or their sum overflows, it will > > cause the value of ja->nr to be incorrect, this will result in the > > allocated memory to ja->buckets being too small, leading to out of > > bounds access in bch2_dev_journal_init. > > > > Reported-by: syzbot+47ecc948aadfb2ab3...@syzkaller.appspotmail.com > > Signed-off-by: Lizhi Xu <lizhi...@windriver.com> > > --- > > fs/bcachefs/journal_sb.c | 16 +++++++++++++++- > > 1 file changed, 15 insertions(+), 1 deletion(-) > > > > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c > > index db80e506e3ab..230ed99130e4 100644 > > --- a/fs/bcachefs/journal_sb.c > > +++ b/fs/bcachefs/journal_sb.c > > @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb > > *sb, struct bch_sb_field *f > > unsigned nr; > > unsigned i; > > struct u64_range *b; > > + u64 total_nr = 0, entry_nr; > > > > nr = bch2_sb_field_journal_v2_nr_entries(journal); > > if (!nr) > > @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb > > *sb, struct bch_sb_field *f > > return -BCH_ERR_ENOMEM_sb_journal_v2_validate; > > > > for (i = 0; i < nr; i++) { > > + entry_nr = le64_to_cpu(journal->d[i].nr); > > + if (entry_nr > UINT_MAX) { > > + prt_printf(err, "Journal v2 entry d[%u] nr %llu > > overflow\n", > > + i, entry_nr); > > + goto err; > > + } > > This check is unnecessary; we know the sum can't overflow a u64 because > we're also checking that the entries are nonoverlapping. You didn't read my previous email carefully. In this issue, journal->d[0] is 7, journal->d[1] is 18446744073709551615, so the sum of their u64 type values will definitely overflow. > > > + total_nr += entry_nr; > > b[i].start = le64_to_cpu(journal->d[i].start); > > - b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr); > > + b[i].end = b[i].start + entry_nr; > > + } > > + > > + if (total_nr > UINT_MAX) { > > + prt_printf(err, "Sum of journal v2 entries nr %llu overflow\n", > > + total_nr); > > + goto err; > > } > > > > sort(b, nr, sizeof(*b), u64_range_cmp, NULL); > > --
BR, Lizhi