From 3822743dc20386d9897e999dbb990befa3a5b3f8 Mon Sep 17 00:00:00 2001 From: Helen Koike Date: Tue, 17 Mar 2026 11:23:10 -0300 Subject: ext4: reject mount if bigalloc with s_first_data_block != 0 bigalloc with s_first_data_block != 0 is not supported, reject mounting it. Signed-off-by: Helen Koike Suggested-by: Theodore Ts'o Reported-by: syzbot+b73703b873a33d8eb8f6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b73703b873a33d8eb8f6 Link: https://patch.msgid.link/20260317142325.135074-1-koike@igalia.com Signed-off-by: Theodore Ts'o Cc: stable@kernel.org --- fs/ext4/super.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 43f680c750ae..152c58fe8e01 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3633,6 +3633,13 @@ int ext4_feature_set_ok(struct super_block *sb, int readonly) "extents feature\n"); return 0; } + if (ext4_has_feature_bigalloc(sb) && + le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) { + ext4_msg(sb, KERN_WARNING, + "bad geometry: bigalloc file system with non-zero " + "first_data_block\n"); + return 0; + } #if !IS_ENABLED(CONFIG_QUOTA) || !IS_ENABLED(CONFIG_QFMT_V2) if (!readonly && (ext4_has_feature_quota(sb) || -- cgit v1.2.3