[PATCH V2] bcachefs: Add journal v2 entry nr value check

[Lizhi Xu]

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+47ecc948aadfb2ab3efc@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
---
 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;
+		}
 	}
 
 	sort(b, nr, sizeof(*b), u64_range_cmp, NULL);
-- 
2.43.0