Re: [syzbot] general protection fault in __copy_super

[syzbot <syzbot+18a5c5e8a9c856944876@syzkaller.appspotmail.com>]

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Subject: general protection fault in __copy_super
Author: djahchankoike@gmail.com

#syz test

__bch2_read_super may return no error code when a corrupt backup
superblock has matching offsets with default opts, the superblock
is freed and is later dereferenced causing a fault. Assign EINVALID
when checking sb offsets.

Signed-off-by: Diogo Jahchan Koike <djahchankoike@gmail.com>
---
 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