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kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load

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The current code uses the sh_offset field in purgatory_info->sechdrs to
store a pointer to the current load address of the section.  Depending
whether the section will be loaded or not this is either a pointer into
purgatory_info->purgatory_buf or kexec_purgatory.  This is not only a
violation of the ELF standard but also makes the code very hard to
understand as you cannot tell if the memory you are using is read-only
or not.

Remove this misuse and store the offset of the section in
pugaroty_info->purgatory_buf in sh_offset.

Link: http://lkml.kernel.org/r/20180321112751.22196-10-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Philipp Rudo 2018-04-13 15:36:39 -07:00 committed by Linus Torvalds
parent 620f697cc2
commit 8da0b72495
2 changed files with 13 additions and 34 deletions
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10
arch/x86/kernel/machine_kexec_64.c
View File

@ -417,13 +417,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
* rel[i].r_offset contains byte offset from beginning
* of section to the storage unit affected.
*
* This is location to update (->sh_offset). This is temporary
* buffer where section is currently loaded. This will finally
* be loaded to a different address later, pointed to by
* This is location to update. This is temporary buffer
* where section is currently loaded. This will finally be
* loaded to a different address later, pointed to by
* ->sh_addr. kexec takes care of moving it
* (kexec_load_segment()).
*/
location = (void *)(section->sh_offset + rel[i].r_offset);
location = pi->purgatory_buf;
location += section->sh_offset;
location += rel[i].r_offset;
/* Final address of the location */
address = section->sh_addr + rel[i].r_offset;

37
kernel/kexec_file.c
View File

@ -790,6 +790,10 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
Elf_Shdr *sechdrs;
int i;
/*
* The section headers in kexec_purgatory are read-only. In order to
* have them modifiable make a temporary copy.
*/
sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
if (!sechdrs)
return -ENOMEM;
@ -797,28 +801,6 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
pi->ehdr->e_shnum * sizeof(Elf_Shdr));
pi->sechdrs = sechdrs;
/*
* We seem to have multiple copies of sections. First copy is which
* is embedded in kernel in read only section. Some of these sections
* will be copied to a temporary buffer and relocated. And these
* sections will finally be copied to their final destination at
* segment load time.
*
* Use ->sh_offset to reflect section address in memory. It will
* point to original read only copy if section is not allocatable.
* Otherwise it will point to temporary copy which will be relocated.
*
* Use ->sh_addr to contain final address of the section where it
* will go during execution time.
*/
for (i = 0; i < pi->ehdr->e_shnum; i++) {
if (sechdrs[i].sh_type == SHT_NOBITS)
continue;
sechdrs[i].sh_offset = (unsigned long)pi->ehdr +
sechdrs[i].sh_offset;
}
offset = 0;
bss_addr = kbuf->mem + kbuf->bufsz;
kbuf->image->start = pi->ehdr->e_entry;
@ -847,17 +829,12 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
kbuf->image->start += kbuf->mem + offset;
}
src = (void *)sechdrs[i].sh_offset;
src = (void *)pi->ehdr + sechdrs[i].sh_offset;
dst = pi->purgatory_buf + offset;
memcpy(dst, src, sechdrs[i].sh_size);
sechdrs[i].sh_addr = kbuf->mem + offset;
/*
* This section got copied to temporary buffer. Update
* ->sh_offset accordingly.
*/
sechdrs[i].sh_offset = (unsigned long)dst;
sechdrs[i].sh_offset = offset;
offset += sechdrs[i].sh_size;
}
@ -1067,7 +1044,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
return -EINVAL;
}
sym_buf = (char *)sec->sh_offset + sym->st_value;
sym_buf = (char *)pi->purgatory_buf + sec->sh_offset + sym->st_value;
if (get_value)
memcpy((void *)buf, sym_buf, size);