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Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 pti updates from Ingo Molnar:
 "The main changes:

   - Make the IBPB barrier more strict and add STIBP support (Jiri
     Kosina)

   - Micro-optimize and clean up the entry code (Andy Lutomirski)

   - ... plus misc other fixes"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/speculation: Propagate information about RSB filling mitigation to sysfs
  x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation
  x86/speculation: Apply IBPB more strictly to avoid cross-process data leak
  x86/speculation: Add RETPOLINE_AMD support to the inline asm CALL_NOSPEC variant
  x86/CPU: Fix unused variable warning when !CONFIG_IA32_EMULATION
  x86/pti/64: Remove the SYSCALL64 entry trampoline
  x86/entry/64: Use the TSS sp2 slot for SYSCALL/SYSRET scratch space
  x86/entry/64: Document idtentry
This commit is contained in:
Linus Torvalds
2018-10-23 18:43:04 +01:00
parent d7197a5ad8 bb4b3b7762
commit d82924c3b8
19 changed files with 222 additions and 176 deletions
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31
arch/x86/mm/tlb.c
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@@ -7,6 +7,7 @@
#include <linux/export.h>
#include <linux/cpu.h>
#include <linux/debugfs.h>
#include <linux/ptrace.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
@@ -180,6 +181,19 @@ static void sync_current_stack_to_mm(struct mm_struct *mm)
}
}
static bool ibpb_needed(struct task_struct *tsk, u64 last_ctx_id)
{
/*
* Check if the current (previous) task has access to the memory
* of the @tsk (next) task. If access is denied, make sure to
* issue a IBPB to stop user->user Spectre-v2 attacks.
*
* Note: __ptrace_may_access() returns 0 or -ERRNO.
*/
return (tsk && tsk->mm && tsk->mm->context.ctx_id != last_ctx_id &&
ptrace_may_access_sched(tsk, PTRACE_MODE_SPEC_IBPB));
}
void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
@@ -286,18 +300,13 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
* one process from doing Spectre-v2 attacks on another.
*
* As an optimization, flush indirect branches only when
* switching into processes that disable dumping. This
* protects high value processes like gpg, without having
* too high performance overhead. IBPB is *expensive*!
*
* This will not flush branches when switching into kernel
* threads. It will also not flush if we switch to idle
* thread and back to the same process. It will flush if we
* switch to a different non-dumpable process.
* switching into a processes that can't be ptrace by the
* current one (as in such case, attacker has much more
* convenient way how to tamper with the next process than
* branch buffer poisoning).
*/
if (tsk && tsk->mm &&
tsk->mm->context.ctx_id != last_ctx_id &&
get_dumpable(tsk->mm) != SUID_DUMP_USER)
if (static_cpu_has(X86_FEATURE_USE_IBPB) &&
ibpb_needed(tsk, last_ctx_id))
indirect_branch_prediction_barrier();
if (IS_ENABLED(CONFIG_VMAP_STACK)) {