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RISC-V Fixes for 5.17-rc8

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* A fix to prevent users from enabling the alternatives framework (and
   thus errata handling) on XIP kernels, where runtime code patching does
   not function correctly.
 * A fix to properly detect offset overflow for AUIPC-based relocations
   in modules.  This may manifest as modules calling arbitrary invalid
   addresses, depending on the address allocated when a module is loaded.
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Merge tag 'riscv-for-linus-5.17-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - prevent users from enabling the alternatives framework (and thus
   errata handling) on XIP kernels, where runtime code patching does not
   function correctly.

 - properly detect offset overflow for AUIPC-based relocations in
   modules. This may manifest as modules calling arbitrary invalid
   addresses, depending on the address allocated when a module is
   loaded.

* tag 'riscv-for-linus-5.17-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Fix auipc+jalr relocation range checks
  riscv: alternative only works on !XIP_KERNEL
This commit is contained in:
Linus Torvalds 2022-03-11 12:28:21 -08:00
commit 77fe1ba902
3 changed files with 19 additions and 7 deletions
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1
arch/riscv/Kconfig.erratas
View file

@ -2,6 +2,7 @@ menu "CPU errata selection"
config RISCV_ERRATA_ALTERNATIVE
bool "RISC-V alternative scheme"
depends on !XIP_KERNEL
default y
help
This Kconfig allows the kernel to automatically patch the

4
arch/riscv/Kconfig.socs
View file

@ -14,8 +14,8 @@ config SOC_SIFIVE
select CLK_SIFIVE
select CLK_SIFIVE_PRCI
select SIFIVE_PLIC
select RISCV_ERRATA_ALTERNATIVE
select ERRATA_SIFIVE
select RISCV_ERRATA_ALTERNATIVE if !XIP_KERNEL
select ERRATA_SIFIVE if !XIP_KERNEL
help
This enables support for SiFive SoC platform hardware.

21
arch/riscv/kernel/module.c
View file

@ -13,6 +13,19 @@
#include <linux/pgtable.h>
#include <asm/sections.h>
/*
* The auipc+jalr instruction pair can reach any PC-relative offset
* in the range [-2^31 - 2^11, 2^31 - 2^11)
*/
static bool riscv_insn_valid_32bit_offset(ptrdiff_t val)
{
#ifdef CONFIG_32BIT
return true;
#else
return (-(1L << 31) - (1L << 11)) <= val && val < ((1L << 31) - (1L << 11));
#endif
}
static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
{
if (v != (u32)v) {
@ -95,7 +108,7 @@ static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
ptrdiff_t offset = (void *)v - (void *)location;
s32 hi20;
if (offset != (s32)offset) {
if (!riscv_insn_valid_32bit_offset(offset)) {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, (long long)v, location);
@ -197,10 +210,9 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
s32 fill_v = offset;
u32 hi20, lo12;
if (offset != fill_v) {
if (!riscv_insn_valid_32bit_offset(offset)) {
/* Only emit the plt entry if offset over 32-bit range */
if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
offset = module_emit_plt_entry(me, v);
@ -224,10 +236,9 @@ static int apply_r_riscv_call_rela(struct module *me, u32 *location,
Elf_Addr v)
{
ptrdiff_t offset = (void *)v - (void *)location;
s32 fill_v = offset;
u32 hi20, lo12;
if (offset != fill_v) {
if (!riscv_insn_valid_32bit_offset(offset)) {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, (long long)v, location);