[PATCH] build_mem_phdrs(): check if p_paddr is invalid

[Dave Young]

On 03/07/17 at 06:53am, Pratyush Anand wrote:
> Hi Simon,
> 
> On Wednesday 01 March 2017 12:43 PM, Dave Young wrote:
> > On 03/01/17 at 11:19am, Pratyush Anand wrote:
> > > Currently, all the p_paddr of PT_LOAD headers are assigned to 0, which
> > > is not correct and could be misleading, since 0 is a valid physical
> > > address.
> > > 
> > > Upstream kernel commit "464920104bf7 /proc/kcore: update physical
> > > address for kcore ram and text" fixed it and now invalid PT_LOAD is
> > > assigned as -1.
> > > 
> > > kexec/arch/i386/crashdump-x86.c:get_kernel_vaddr_and_size() uses kcore
> > > interface and so calls build_mem_phdrs() for kcore PT_LOAD headers.
> > > 
> > > This patch fixes build_mem_phdrs() to check if p_paddr is invalid.
> 
> Any comment on this?

Simon, ping, explain a bit about the background based on the patch log:

Although it is a kernel regression, the original p_addr = 0 assumption is
wrong, it should be fixed in kernel instead of keep it to avoid
kexec-tools breakage.

Since latest kernel already has the fix merged, kexec-tools will fail to
load crash kernel now. 

Any opinion about this patch?
> 
> > > 
> > > Signed-off-by: Pratyush Anand <panand at redhat.com>
> > > ---
> > >  kexec/kexec-elf.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/kexec/kexec-elf.c b/kexec/kexec-elf.c
> > > index 1d6320a2f0e6..be60bbd48486 100644
> > > --- a/kexec/kexec-elf.c
> > > +++ b/kexec/kexec-elf.c
> > > @@ -432,7 +432,8 @@ static int build_mem_phdrs(const char *buf, off_t len, struct mem_ehdr *ehdr,
> > >  			}
> > >  			return -1;
> > >  		}
> > > -		if ((phdr->p_paddr + phdr->p_memsz) < phdr->p_paddr) {
> > > +		if (phdr->p_paddr != (unsigned long long)-1 &&
> > > +			(phdr->p_paddr + phdr->p_memsz) < phdr->p_paddr) {
> > >  			/* The memory address wraps */
> > >  			if (probe_debug) {
> > >  				fprintf(stderr, "ELF address wrap around\n");
> > > --
> > > 2.9.3
> > > 
> > 
> > Acked-by: Dave Young <dyoung at redhat.com>
> > 
> 
> 
> 
> ~Pratyush
> 
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave