OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

s390/kdump: Add final note 

Since linux v3.14 with commit 38dfac843c ("vmcore: prevent PT_NOTE
p_memsz overflow during header update") on s390 we get the following
message in the kdump kernel:

  Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x6b6b6b6b,
  n_descsz=0x6b6b6b6b

The reason for this is that we don't create a final zero note in
the ELF header which the proc/vmcore code uses to find out the end
of the notes section (see also kernel/kexec_core.c:final_note()).

It still worked on s390 by chance because we (most of the time?) have the
byte pattern 0x6b6b6b6b after the notes section which also makes the notes
parsing code stop in update_note_header_size_elf64() because 0x6b6b6b6b is
interpreded as note size:

  if ((real_sz + sz) > max_sz) {
          pr_warn("Warning: Exceeded p_memsz, dropping P ...);
          break;
  }

So fix this and add the missing final note to the ELF header.
We don't have to adjust the memory size for ELF header ("alloc_size")
because the new ELF note still fits into the 0x1000 base memory.

Cc: stable@vger.kernel.org # v4.4+
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Michael Holzheu 2017-03-23 21:02:54 +01:00 committed by Martin Schwidefsky
parent 59cea29a34
commit dcc00b79fc
1 changed files with 15 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
arch/s390/kernel/crash_dump.c
View File

@ -428,6 +428,20 @@ static void *nt_vmcoreinfo(void *ptr)
return nt_init_name(ptr, 0, vmcoreinfo, size, "VMCOREINFO");
}
/*
* Initialize final note (needed for /proc/vmcore code)
*/
static void *nt_final(void *ptr)
{
Elf64_Nhdr *note;
note = (Elf64_Nhdr *) ptr;
note->n_namesz = 0;
note->n_descsz = 0;
note->n_type = 0;
return PTR_ADD(ptr, sizeof(Elf64_Nhdr));
}
/*
* Initialize ELF header (new kernel)
*/
@ -515,6 +529,7 @@ static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset)
if (sa->prefix != 0)
ptr = fill_cpu_elf_notes(ptr, cpu++, sa);
ptr = nt_vmcoreinfo(ptr);
ptr = nt_final(ptr);
memset(phdr, 0, sizeof(*phdr));
phdr->p_type = PT_NOTE;
phdr->p_offset = notes_offset;