The patch titled
Subject: kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load
has been added to the -mm tree. Its filename is
kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load.patch
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------------------------------------------------------
From: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx>
Subject: kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load
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@xxxxxxxxxxxxxxxxxx
Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx>
Cc: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/machine_kexec_64.c | 10 ++++---
kernel/kexec_file.c | 37 +++++----------------------
2 files changed, 13 insertions(+), 34 deletions(-)
diff -puN arch/x86/kernel/machine_kexec_64.c~kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load arch/x86/kernel/machine_kexec_64.c
--- a/arch/x86/kernel/machine_kexec_64.c~kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load
+++ a/arch/x86/kernel/machine_kexec_64.c
@@ -417,13 +417,15 @@ int arch_kexec_apply_relocations_add(str
* 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;
diff -puN kernel/kexec_file.c~kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load kernel/kexec_file.c
--- a/kernel/kexec_file.c~kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load
+++ a/kernel/kexec_file.c
@@ -832,6 +832,10 @@ static int kexec_purgatory_setup_sechdrs
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;
@@ -839,28 +843,6 @@ static int kexec_purgatory_setup_sechdrs
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;
@@ -889,17 +871,12 @@ static int kexec_purgatory_setup_sechdrs
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;
}
@@ -1109,7 +1086,7 @@ int kexec_purgatory_get_set_symbol(struc
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);
_
Patches currently in -mm which might be from prudo@xxxxxxxxxxxxxxxxxx are
kexec_file-silence-compile-warnings.patch
kexec_file-remove-checks-in-kexec_purgatory_load.patch
kexec_file-make-purgatory_info-ehdr-const.patch
kexec_file-search-symbols-in-read-only-kexec_purgatory.patch
kexec_file-use-read-only-sections-in-arch_kexec_apply_relocations.patch
kexec_file-split-up-__kexec_load_puragory.patch
kexec_file-remove-unneeded-for-loop-in-kexec_purgatory_setup_sechdrs.patch
kexec_file-remove-unneeded-variables-in-kexec_purgatory_setup_sechdrs.patch
kexec_file-remove-mis-use-of-sh_offset-field-during-purgatory-load.patch
kexec_file-allow-archs-to-set-purgatory-load-address.patch
kexec_file-move-purgatories-sha256-to-common-code.patch
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