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Date: Tue, 30 Apr 2019 04:22:06 -0700
From: tip-bot for Nadav Amit <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: peterz@...radead.org, namit@...are.com, mingo@...nel.org,
akpm@...ux-foundation.org, tglx@...utronix.de,
rick.p.edgecombe@...el.com, hpa@...or.com, ard.biesheuvel@...aro.org,
dave.hansen@...ux.intel.com, torvalds@...ux-foundation.org,
kristen@...ux.intel.com, linux_dti@...oud.com, bp@...en8.de,
deneen.t.dock@...el.com, riel@...riel.com, luto@...nel.org,
will.deacon@....com, kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org
Subject: [tip:x86/mm] x86/kprobes: Set instruction page as executable
Commit-ID: 7298e24f904224fa79eb8fd7e0fbd78950ccf2db
Gitweb: https://git.kernel.org/tip/7298e24f904224fa79eb8fd7e0fbd78950ccf2db
Author: Nadav Amit <namit@...are.com>
AuthorDate: Thu, 25 Apr 2019 17:11:30 -0700
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 30 Apr 2019 12:37:54 +0200
x86/kprobes: Set instruction page as executable
Set the page as executable after allocation. This patch is a
preparatory patch for a following patch that makes module allocated
pages non-executable.
While at it, do some small cleanup of what appears to be unnecessary
masking.
Signed-off-by: Nadav Amit <namit@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <akpm@...ux-foundation.org>
Cc: <ard.biesheuvel@...aro.org>
Cc: <deneen.t.dock@...el.com>
Cc: <kernel-hardening@...ts.openwall.com>
Cc: <kristen@...ux.intel.com>
Cc: <linux_dti@...oud.com>
Cc: <will.deacon@....com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Rik van Riel <riel@...riel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/20190426001143.4983-11-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
arch/x86/kernel/kprobes/core.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index fed46ddb1eef..06058c44ab57 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -431,8 +431,20 @@ void *alloc_insn_page(void)
void *page;
page = module_alloc(PAGE_SIZE);
- if (page)
- set_memory_ro((unsigned long)page & PAGE_MASK, 1);
+ if (!page)
+ return NULL;
+
+ /*
+ * First make the page read-only, and only then make it executable to
+ * prevent it from being W+X in between.
+ */
+ set_memory_ro((unsigned long)page, 1);
+
+ /*
+ * TODO: Once additional kernel code protection mechanisms are set, ensure
+ * that the page was not maliciously altered and it is still zeroed.
+ */
+ set_memory_x((unsigned long)page, 1);
return page;
}
@@ -440,8 +452,12 @@ void *alloc_insn_page(void)
/* Recover page to RW mode before releasing it */
void free_insn_page(void *page)
{
- set_memory_nx((unsigned long)page & PAGE_MASK, 1);
- set_memory_rw((unsigned long)page & PAGE_MASK, 1);
+ /*
+ * First make the page non-executable, and 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);
}
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