This is a note to let you know that I've just added the patch titled
x86/syscall: Sanitize syscall table de-references under speculation
to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86syscall_Sanitize_syscall_table_de-references_under_speculation.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
Subject: x86/syscall: Sanitize syscall table de-references under speculation
From: Dan Williams dan.j.williams@xxxxxxxxx
Date: Mon Jan 29 17:02:59 2018 -0800
From: Dan Williams dan.j.williams@xxxxxxxxx
commit 2fbd7af5af8665d18bcefae3e9700be07e22b681
The syscall table base is a user controlled function pointer in kernel
space. Use array_index_nospec() to prevent any out of bounds speculation.
While retpoline prevents speculating into a userspace directed target it
does not stop the pointer de-reference, the concern is leaking memory
relative to the syscall table base, by observing instruction cache
behavior.
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: kernel-hardening@xxxxxxxxxxxxxxxxxx
Cc: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: alan@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/common.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -21,6 +21,7 @@
#include <linux/export.h>
#include <linux/context_tracking.h>
#include <linux/user-return-notifier.h>
+#include <linux/nospec.h>
#include <linux/uprobes.h>
#include <linux/livepatch.h>
#include <linux/syscalls.h>
@@ -282,7 +283,8 @@ __visible void do_syscall_64(struct pt_r
* regs->orig_ax, which changes the behavior of some syscalls.
*/
if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
- regs->ax = sys_call_table[nr & __SYSCALL_MASK](
+ nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls);
+ regs->ax = sys_call_table[nr](
regs->di, regs->si, regs->dx,
regs->r10, regs->r8, regs->r9);
}
@@ -318,6 +320,7 @@ static __always_inline void do_syscall_3
}
if (likely(nr < IA32_NR_syscalls)) {
+ nr = array_index_nospec(nr, IA32_NR_syscalls);
/*
* It's possible that a 32-bit syscall implementation
* takes a 64-bit parameter but nonetheless assumes that
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-4.15/objtool_Add_support_for_alternatives_at_the_end_of_a_section.patch
queue-4.15/x86pti_Do_not_enable_PTI_on_CPUs_which_are_not_vulnerable_to_Meltdown.patch
queue-4.15/x86_Introduce_barrier_nospec.patch
queue-4.15/x86speculation_Use_Indirect_Branch_Prediction_Barrier_in_context_switch.patch
queue-4.15/x86get_user_Use_pointer_masking_to_limit_speculation.patch
queue-4.15/x86_Introduce___uaccess_begin_nospec()_and_uaccess_try_nospec.patch
queue-4.15/x86cpufeature_Blacklist_SPEC_CTRLPRED_CMD_on_early_Spectre_v2_microcodes.patch
queue-4.15/x86cpufeatures_Add_Intel_feature_bits_for_Speculation_Control.patch
queue-4.15/x86paravirt_Remove_noreplace-paravirt_cmdline_option.patch
queue-4.15/KVM_VMX_Make_indirect_call_speculation_safe.patch
queue-4.15/x86msr_Add_definitions_for_new_speculation_control_MSRs.patch
queue-4.15/x86alternative_Print_unadorned_pointers.patch
queue-4.15/KVMVMX_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch
queue-4.15/x86cpufeatures_Add_CPUID_7_EDX_CPUID_leaf.patch
queue-4.15/array_index_nospec_Sanitize_speculative_array_de-references.patch
queue-4.15/Documentation_Document_array_index_nospec.patch
queue-4.15/x86entry64_Remove_the_SYSCALL64_fast_path.patch
queue-4.15/x86bugs_Drop_one_mitigation_from_dmesg.patch
queue-4.15/x86cpufeatures_Add_AMD_feature_bits_for_Speculation_Control.patch
queue-4.15/KVMSVM_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch
queue-4.15/x86asm_Move_status_from_thread_struct_to_thread_info.patch
queue-4.15/KVMx86_Add_IBPB_support.patch
queue-4.15/x86_Implement_array_index_mask_nospec.patch
queue-4.15/KVMVMX_Emulate_MSR_IA32_ARCH_CAPABILITIES.patch
queue-4.15/nl80211_Sanitize_array_index_in_parse_txq_params.patch
queue-4.15/moduleretpoline_Warn_about_missing_retpoline_in_module.patch
queue-4.15/x86speculation_Add_basic_IBPB_(Indirect_Branch_Prediction_Barrier)_support.patch
queue-4.15/x86speculation_Simplify_indirect_branch_prediction_barrier().patch
queue-4.15/x86nospec_Fix_header_guards_names.patch
queue-4.15/KVM_x86_Make_indirect_calls_in_emulator_speculation_safe.patch
queue-4.15/x86uaccess_Use___uaccess_begin_nospec()_and_uaccess_try_nospec.patch
queue-4.15/x86entry64_Push_extra_regs_right_away.patch
queue-4.15/x86usercopy_Replace_open_coded_stacclac_with___uaccess_begin_end.patch
queue-4.15/vfs_fdtable_Prevent_bounds-check_bypass_via_speculative_execution.patch
queue-4.15/x86retpoline_Simplify_vmexit_fill_RSB().patch
queue-4.15/objtool_Warn_on_stripped_section_symbol.patch
queue-4.15/x86spectre_Report_get_user_mitigation_for_spectre_v1.patch
queue-4.15/x86cpufeatures_Clean_up_Spectre_v2_related_CPUID_flags.patch
queue-4.15/x86syscall_Sanitize_syscall_table_de-references_under_speculation.patch
queue-4.15/objtool_Improve_retpoline_alternative_handling.patch