Patch "objtool: Fix segfault in ignore_unreachable_insn()" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

objtool: Fix segfault in ignore_unreachable_insn()

to the 4.14-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:
objtool-fix-segfault-in-ignore_unreachable_insn.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Josh Poimboeuf <[email protected]>
Date: Thu, 8 Feb 2018 17:09:25 -0600
Subject: objtool: Fix segfault in ignore_unreachable_insn()

From: Josh Poimboeuf <[email protected]>

commit fe24e27128252c230a34a6c628da2bf1676781ea upstream.

Peter Zijlstra's patch for converting WARN() to use UD2 triggered a bunch of false "unreachable instruction" warnings, which then triggered a seg fault in ignore_unreachable_insn().

The seg fault happened when it tried to dereference a NULL 'insn->func' pointer. Thanks to static_cpu_has(), some functions can jump to a non-function area in the .altinstr_aux section. That breaks ignore_unreachable_insn()'s assumption that it's always inside the original function.

Make sure ignore_unreachable_insn() only follows jumps within the current function.

---
 tools/objtool/check.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

@@ -1935,13 +1935,19 @@ static bool ignore_unreachable_insn(stru
 		if (is_kasan_insn(insn) || is_ubsan_insn(insn))
 			return true;
 
-		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
-			insn = insn->jump_dest;
-			continue;
+		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
+			if (insn->jump_dest &&
+			    insn->jump_dest->func == insn->func) {
+				insn = insn->jump_dest;
+				continue;
+			}
+
+			break;
 		}
 
 		if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
 			break;
+
 		insn = list_next_entry(insn, list);
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/x86-entry-64-interleave-xor-register-clearing-with-push-instructions.patch queue-4.14/x86-entry-64-merge-the-pop_c_regs-and-pop_extra_regs-macros-into-a-single-pop_regs-macro.patch queue-4.14/x86-entry-64-remove-the-unused-icebp-macro.patch queue-4.14/kvm-nvmx-set-the-cpu_based_use_msr_bitmaps-if-we-have-a-valid-l02-msr-bitmap.patch queue-4.14/x86-nvmx-properly-set-spec_ctrl-and-pred_cmd-before-merging-msrs.patch queue-4.14/x86-speculation-add-asm-msr-index.h-dependency.patch queue-4.14/x86-entry-64-use-push_and_clean_regs-in-more-cases.patch queue-4.14/x86-debug-use-ud2-for-warn.patch queue-4.14/x86-entry-64-fix-paranoid_entry-frame-pointer-warning.patch queue-4.14/x86-speculation-update-speculation-control-microcode-blacklist.patch queue-4.14/x86-entry-64-clear-registers-for-exceptions-interrupts-to-reduce-speculation-attack-surface.patch queue-4.14/x86-speculation-correct-speculation-control-microcode-blacklist-again.patch queue-4.14/x86-entry-64-merge-save_c_regs-and-save_extra_regs-remove-unused-extensions.patch queue-4.14/x86-debug-objtool-annotate-warn-related-ud2-as-reachable.patch queue-4.14/objtool-fix-segfault-in-ignore_unreachable_insn.patch queue-4.14/x86-entry-64-indent-push_and_clear_regs-and-pop_regs-properly.patch queue-4.14/x86-entry-64-clear-extra-registers-beyond-syscall-arguments-to-reduce-speculation-attack-surface.patch queue-4.14/kvm-x86-reduce-retpoline-performance-impact-in-slot_handle_level_range-by-always-inlining-iterator-helper-methods.patch queue-4.14/x86-mm-pti-fix-pti-comment-in-entry_syscall_64.patch queue-4.14/x86-entry-64-get-rid-of-the-alloc_pt_gpregs_on_stack-and-save_and_clear_regs-macros.patch queue-4.14/x86-speculation-clean-up-various-spectre-related-details.patch queue-4.14/x86-entry-64-introduce-the-push_and_clean_regs-macro.patch queue-4.14/revert-x86-speculation-simplify-indirect_branch_prediction_barrier.patch queue-4.14/x86-entry-64-compat-clear-registers-for-compat-syscalls-to-reduce-speculation-attack-surface.patch queue-4.14/x86-mm-rename-flush_tlb_single-and-flush_tlb_one-to-__flush_tlb_one_.patch queue-4.14/x86-entry-64-fix-cr3-restore-in-paranoid_exit.patch