syzbot reported a null ptr deref in __copy_user [0] In __bch2_read_super, when a corrupt backup superblock matches the default opts offset, no error is assigned to ret and the freed superblock gets through, possibly being assigned as the best sb in bch2_fs_open and being later dereferenced, causing a fault. Assign EINVALID to ret when iterating through layout.
[0]: https://syzkaller.appspot.com/bug?extid=18a5c5e8a9c856944876 Reported-by: [email protected] Closes: https://syzkaller.appspot.com/bug?extid=18a5c5e8a9c856944876 Signed-off-by: Diogo Jahchan Koike <[email protected]> --- fs/bcachefs/super-io.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c index c8c2ccbdfbb5..fbca0bd302db 100644 --- a/fs/bcachefs/super-io.c +++ b/fs/bcachefs/super-io.c @@ -796,8 +796,10 @@ static int __bch2_read_super(const char *path, struct bch_opts *opts, i < layout.sb_offset + layout.nr_superblocks; i++) { offset = le64_to_cpu(*i); - if (offset == opt_get(*opts, sb)) + if (offset == opt_get(*opts, sb)) { + ret = -BCH_ERR_invalid; continue; + } ret = read_one_super(sb, offset, &err); if (!ret) -- 2.43.0
