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X86 core updates:

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- Prevent kprobes on compiler generated CFI checking code.
 
     The compiler generates a instruction sequence for indirect call
     checks. If this sequence is modified with a kprobe, then the check
     fails. So the instructions must be protected against probing.
 
   - A few minor cleanups for the SMP code
 
 Thanks,
 
 	tglx
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Merge tag 'x86-core-2023-08-30-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 core updates from Thomas Gleixner:

 - Prevent kprobes on compiler generated CFI checking code.

   The compiler generates an instruction sequence for indirect call
   checks. If this sequence is modified with a kprobe, then the check
   fails. So the instructions must be protected against probing.

 - A few minor cleanups for the SMP code

* tag 'x86-core-2023-08-30-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/kprobes: Prohibit probing on compiler generated CFI checking code
  x86/smpboot: Change smp_store_boot_cpu_info() to static
  x86/smp: Remove a non-existent function declaration
  x86/smpboot: Remove a stray comment about CPU hotplug
This commit is contained in:
Linus Torvalds 2023-08-30 10:10:31 -07:00
commit 87fa732dc5
4 changed files with 39 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/include/asm/smp.h
View File

@ -132,11 +132,8 @@ void smp_kick_mwait_play_dead(void);
void native_smp_send_reschedule(int cpu);
void native_send_call_func_ipi(const struct cpumask *mask);
void native_send_call_func_single_ipi(int cpu);
void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);
bool smp_park_other_cpus_in_init(void);
void smp_store_boot_cpu_info(void);
void smp_store_cpu_info(int id);
asmlinkage __visible void smp_reboot_interrupt(void);

34
arch/x86/kernel/kprobes/core.c
View File

@ -45,6 +45,7 @@
#include <linux/vmalloc.h>
#include <linux/pgtable.h>
#include <linux/set_memory.h>
#include <linux/cfi.h>
#include <asm/text-patching.h>
#include <asm/cacheflush.h>
@ -293,7 +294,40 @@ static int can_probe(unsigned long paddr)
#endif
addr += insn.length;
}
if (IS_ENABLED(CONFIG_CFI_CLANG)) {
/*
* The compiler generates the following instruction sequence
* for indirect call checks and cfi.c decodes this;
*
*  movl -<id>, %r10d ; 6 bytes
* addl -4(%reg), %r10d ; 4 bytes
* je .Ltmp1 ; 2 bytes
* ud2 ; <- regs->ip
* .Ltmp1:
*
* Also, these movl and addl are used for showing expected
* type. So those must not be touched.
*/
__addr = recover_probed_instruction(buf, addr);
if (!__addr)
return 0;
if (insn_decode_kernel(&insn, (void *)__addr) < 0)
return 0;
if (insn.opcode.value == 0xBA)
offset = 12;
else if (insn.opcode.value == 0x3)
offset = 6;
else
goto out;
/* This movl/addl is used for decoding CFI. */
if (is_cfi_trap(addr + offset))
return 0;
}
out:
return (addr == paddr);
}

6
arch/x86/kernel/smpboot.c
View File

@ -414,7 +414,7 @@ found:
return 0;
}
void __init smp_store_boot_cpu_info(void)
static void __init smp_store_boot_cpu_info(void)
{
int id = 0; /* CPU 0 */
struct cpuinfo_x86 *c = &cpu_data(id);
@ -1601,9 +1601,7 @@ void play_dead_common(void)
idle_task_exit();
cpuhp_ap_report_dead();
/*
* With physical CPU hotplug, we should halt the cpu
*/
local_irq_disable();
}

4
include/linux/cfi.h
View File

@ -19,11 +19,13 @@ static inline enum bug_trap_type report_cfi_failure_noaddr(struct pt_regs *regs,
{
return report_cfi_failure(regs, addr, NULL, 0);
}
#endif /* CONFIG_CFI_CLANG */
#ifdef CONFIG_ARCH_USES_CFI_TRAPS
bool is_cfi_trap(unsigned long addr);
#else
static inline bool is_cfi_trap(unsigned long addr) { return false; }
#endif
#endif /* CONFIG_CFI_CLANG */
#ifdef CONFIG_MODULES
#ifdef CONFIG_ARCH_USES_CFI_TRAPS