Re: [PATCHv2 2/2] kernel/kexec: Fix IMA when allocation happens in CMA area

[Baoquan He <bhe@redhat.com>]

On 11/07/25 at 01:13pm, Pingfan Liu wrote:
> On Fri, Nov 7, 2025 at 9:51 AM Baoquan He <bhe@redhat.com> wrote:
> >
> > On 11/06/25 at 06:01pm, Pingfan Liu wrote:
> > > On Thu, Nov 6, 2025 at 4:01 PM Baoquan He <bhe@redhat.com> wrote:
> > > >
> > > > On 11/06/25 at 02:59pm, Pingfan Liu wrote:
> > > > > When I tested kexec with the latest kernel, I ran into the following warning:
> > > > >
> > > > > [   40.712410] ------------[ cut here ]------------
> > > > > [   40.712576] WARNING: CPU: 2 PID: 1562 at kernel/kexec_core.c:1001 kimage_map_segment+0x144/0x198
> > > > > [...]
> > > > > [   40.816047] Call trace:
> > > > > [   40.818498]  kimage_map_segment+0x144/0x198 (P)
> > > > > [   40.823221]  ima_kexec_post_load+0x58/0xc0
> > > > > [   40.827246]  __do_sys_kexec_file_load+0x29c/0x368
> > > > > [...]
> > > > > [   40.855423] ---[ end trace 0000000000000000 ]---
> > > > >
> > > > > This is caused by the fact that kexec allocates the destination directly
> > > > > in the CMA area. In that case, the CMA kernel address should be exported
> > > > > directly to the IMA component, instead of using the vmalloc'd address.
> > > >
> > > > Well, you didn't update the log accordingly.
> > > >
> > >
> > > I am not sure what you mean. Do you mean the earlier content which I
> > > replied to you?
> >
> > No. In v1, you return cma directly. But in v2, you return its direct
> > mapping address, isnt' it?
> >
> 
> Yes. But I think it is a fault in the code, which does not convey the
> expression in the commit log. Do you think I should rephrase the words
> "the CMA kernel address" as "the CMA kernel direct mapping address"?

That's fine to me.

> 
> > >
> > > > Do you know why cma area can't be mapped into vmalloc?
> > > >
> > > Should not the kernel direct mapping be used?
> >
> > When image->segment_cma[i] has value, image->ima_buffer_addr also
> > contains the physical address of the cma area, why cma physical address
> > can't be mapped into vmalloc and cause the failure and call trace?
> >
> 
> It could be done using the vmalloc approach, but it's unnecessary.
> IIUC, kimage_map_segment() was introduced to provide a contiguous
> virtual address for IMA access, since the IND_SRC pages are scattered
> throughout the kernel. However, in the CMA case, there is already a
> contiguous virtual address in the kernel direct mapping range.
> Normally, when we have a physical address, we simply use
> phys_to_virt() to get its corresponding kernel virtual address.

OK, I understand cma area is contiguous, and no need to map into
vmalloc. I am wondering why in the old code mapping cma addrss into 
vmalloc cause the warning which you said is a IMA problem.