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SubjectRe: [PATCH V2] x86/kexec: fix a kexec_file_load failure
On 01/08/19 at 01:24pm, Baoquan He wrote:
> On 12/28/18 at 09:12am, Dave Young wrote:
> > The code cleanup mentioned in Fixes tag changed the behavior of
> > kexec_locate_mem_hole. The kexec_locate_mem_hole will try to
> > allocate free memory only when kbuf.mem is initialized as zero.
> >
> > But in x86 kexec_file_load implementation there are a few places
> > the kbuf.mem is reused like below:
> > /* kbuf initialized, kbuf.mem = 0 */
> > ...
> > kexec_add_buffer()
> > ...
> > kexec_add_buffer()
> >
> > The second kexec_add_buffer will reuse previous kbuf but not
> > reinitialize the kbuf.mem.
> >
> > Thus kexec_file_load failed because the sanity check failed.
> >
> > So explictily reset kbuf.mem to fix the issue.
> >
> > Fixes: b6664ba42f14 ("s390, kexec_file: drop arch_kexec_mem_walk()")
> > Signed-off-by: Dave Young <dyoung@redhat.com>
> > Cc: <stable@vger.kernel.org>
> > ---
> > V1 -> V2: use KEXEC_BUF_MEM_UNKNOWN in code.
> > arch/x86/kernel/crash.c | 1 +
> > arch/x86/kernel/kexec-bzimage64.c | 2 ++
> > 2 files changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> > index f631a3f15587..6b7890c7889b 100644
> > --- a/arch/x86/kernel/crash.c
> > +++ b/arch/x86/kernel/crash.c
> > @@ -469,6 +469,7 @@ int crash_load_segments(struct kimage *image)
> >
>
> Wondering why this place doesn't need the initialization assignment.
> Isn't it to assign in all places before kexec_add_buffer() calling?

C designated initializers will make sure to initialize it as zero.
We set KEXEC_BUF_MEM_UNKNOWN as 0 so it just works.

>
> /* Add backup segment. */
> if (image->arch.backup_src_sz) {
> }
>
> > kbuf.memsz = kbuf.bufsz;
> > kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
> > + kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> > ret = kexec_add_buffer(&kbuf);
> > if (ret) {
> > vfree((void *)image->arch.elf_headers);
> > diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> > index 278cd07228dd..0d5efa34f359 100644
> > --- a/arch/x86/kernel/kexec-bzimage64.c
> > +++ b/arch/x86/kernel/kexec-bzimage64.c
> > @@ -434,6 +434,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> > kbuf.memsz = PAGE_ALIGN(header->init_size);
> > kbuf.buf_align = header->kernel_alignment;
> > kbuf.buf_min = MIN_KERNEL_LOAD_ADDR;
>
> Same question for bzImage64_load(), there are three kexec_add_buffer()
> calling, I only saw two initialization in this patch.
>
> > + kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> > ret = kexec_add_buffer(&kbuf);
> > if (ret)
> > goto out_free_params;
> > @@ -448,6 +449,7 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> > kbuf.bufsz = kbuf.memsz = initrd_len;
> > kbuf.buf_align = PAGE_SIZE;
> > kbuf.buf_min = MIN_INITRD_LOAD_ADDR;
> > + kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> > ret = kexec_add_buffer(&kbuf);
> > if (ret)
> > goto out_free_params;
> > --
> > 2.17.0
> >

Thanks
Dave

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