Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Date | Tue, 18 May 2021 16:17:53 +0200 | Subject | Re: [PATCH v3 1/4] kexec: simplify compat_sys_kexec_load |
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On Tue, May 18, 2021 at 4:05 PM Arnd Bergmann <arnd@kernel.org> wrote: > > On Tue, May 18, 2021 at 3:41 PM Eric W. Biederman <ebiederm@xmission.com> wrote: > > > > Arnd Bergmann <arnd@kernel.org> writes: > > > > > From: Arnd Bergmann <arnd@arndb.de>KEXEC_ARCH_DEFAULT > > > > > > The compat version of sys_kexec_load() uses compat_alloc_user_space to > > > convert the user-provided arguments into the native format. > > > > > > Move the conversion into the regular implementation with > > > an in_compat_syscall() check to simplify it and avoid the > > > compat_alloc_user_space() call. > > > > > > compat_sys_kexec_load() now behaves the same as sys_kexec_load(). > > > > Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com> > >KEXEC_ARCH_DEFAULT > > The patch is wrong. > > > > The logic between the compat entry point and the ordinary entry point > > are by necessity different. This unifies the logic and breaks the compat > > entry point. > > > > The fundamentally necessity is that the code being loaded needs to know > > which mode the kernel is running in so it can safely transition to the > > new kernel. > > > > Given that the two entry points fundamentally need different logic, > > and that difference was not preserved and the goal of this patchset > > was to unify that which fundamentally needs to be different. I don't > > think this patch series makes any sense for kexec. > > Sorry, I'm not following that explanation. Can you clarify what different > modes of the kernel you are referring to here, and how my patch > changes this?
I think I figured it out now myself after comparing the two functions:
--- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -269,7 +269,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
/* Verify we are on the appropriate architecture */ if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && - ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) + (in_compat_syscall() || + ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))) return -EINVAL;
/* Because we write directly to the reserved memory Not sure if that's the best way of doing it, but it looks like folding this in restores the current behavior.
Arnd
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