[PATCH V3] bcachefs: Add journal v2 entry nr value check

[Lizhi Xu]

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;
+               }
+               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);
-- 
2.43.0