linux-kernel - [PATCH v2 19/20] x86/kprobes: Use vmalloc special flag

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Message-Id: <20190129003422.9328-20-rick.p.edgecombe@intel.com>
Date:   Mon, 28 Jan 2019 16:34:21 -0800
From:   Rick Edgecombe <rick.p.edgecombe@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Nadav Amit <nadav.amit@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, linux_dti@...oud.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, akpm@...ux-foundation.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        will.deacon@....com, ard.biesheuvel@...aro.org,
        kristen@...ux.intel.com, deneen.t.dock@...el.com,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH v2 19/20] x86/kprobes: Use vmalloc special flag

Use new flag VM_HAS_SPECIAL_PERMS for handling freeing of special
permissioned memory in vmalloc and remove places where memory was set NX
and RW before freeing which is no longer needed.

Cc: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
 arch/x86/kernel/kprobes/core.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index fac692e36833..f2fab35bcb82 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -434,6 +434,7 @@ void *alloc_insn_page(void)
 	if (page == NULL)
 		return NULL;
 
+	set_vm_special(page);
 	/*
 	 * First make the page read-only, and then only then make it executable
 	 * to prevent it from being W+X in between.
@@ -452,12 +453,6 @@ void *alloc_insn_page(void)
 /* Recover page to RW mode before releasing it */
 void free_insn_page(void *page)
 {
-	/*
-	 * First make the page non-executable, and then only then make it
-	 * writable to prevent it from being W+X in between.
-	 */
-	set_memory_nx((unsigned long)page, 1);
-	set_memory_rw((unsigned long)page, 1);
 	module_memfree(page);
 }
 
-- 
2.17.1