On Wed, Aug 21, 2024 at 10:33:55AM GMT, Lizhi Xu wrote: > On Tue, 20 Aug 2024 19:34:18 -0400, Kent Overstreet wrote: > > > When journal v2 entry nr overflow, 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 | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c > > > index db80e506e3ab..db2b2100e4e5 100644 > > > --- a/fs/bcachefs/journal_sb.c > > > +++ b/fs/bcachefs/journal_sb.c > > > @@ -119,6 +119,11 @@ static int bch2_sb_journal_v2_validate(struct bch_sb > > > *sb, struct bch_sb_field *f > > > for (i = 0; i < nr; i++) { > > > b[i].start = le64_to_cpu(journal->d[i].start); > > > b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr); > > > + if (le64_to_cpu(journal->d[i].nr) > UINT_MAX) { > > > + prt_printf(err, "journal v2 entry d[%u].nr %llu > > > overflow\n", > > > + i, le64_to_cpu(journal->d[i].nr)); > > > + goto err; > > > + } > > > > no, you need to sum up _all_ the entries and verify the total doesn't > > overflow UINT_MAX > The overflow value of le64_to_cpu(journal->d[i].nr) is > 18446744073709551615(for u64), > or in other words, it is -1 for s64. > > Therefore, the existing check for single entry is retained, and an overflow > check for the total value of all entry is will added.
No, this is completely broken.