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[ Upstream commit 34ab4c75588c07cca12884f2bf6b0347c7a13872 ] syzbot is reporting that S_IFMT bits of inode->i_mode can become bogus when the S_IFMT bits of the 32bits "mode" field loaded from disk are corrupted or when the 32bits "attributes" field loaded from disk are corrupted. A documentation says that BFS uses only lower 9 bits of the "mode" field. But I can't find an explicit explanation that the unused upper 23 bits (especially, the S_IFMT bits) are initialized with 0. Therefore, ignore the S_IFMT bits of the "mode" field loaded from disk. Also, verify that the value of the "attributes" field loaded from disk is either BFS_VREG or BFS_VDIR (because BFS supports only regular files and the root directory). Reported-by: syzbot+895c23f6917da440ed0d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=895c23f6917da440ed0d Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Link: https://patch.msgid.link/fabce673-d5b9-4038-8287-0fd65d80203b@I-love.SAKURA.ne.jp Reviewed-by: Tigran Aivazian <aivazian.tigran@gmail.com> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Ulrich Hecht <uli@kernel.org>