Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
From: Andy Lutomirski <luto@kernel.org>
Date: 2020-09-19 16:22:00
Also in:
io-uring, keyrings, linux-arch, linux-arm-kernel, linux-block, linux-fsdevel, linux-mm, linux-s390, linux-scsi, linux-security-module, linuxppc-dev, lkml, netdev, sparclinux
On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig [off-list ref] wrote:
On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:quoted
Said that, why not provide a variant that would take an explicit "is it compat" argument and use it there? And have the normal one pass in_compat_syscall() to that...That would help to not introduce a regression with this series yes. But it wouldn't fix existing bugs when io_uring is used to access read or write methods that use in_compat_syscall(). One example that I recently ran into is drivers/scsi/sg.c.
Aside from the potentially nasty use of per-task variables, one thing I don't like about PF_FORCE_COMPAT is that it's one-way. If we're going to have a generic mechanism for this, shouldn't we allow a full override of the syscall arch instead of just allowing forcing compat so that a compat syscall can do a non-compat operation?