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Message-Id: <20190221234451.17632-9-rick.p.edgecombe@intel.com>
Date: Thu, 21 Feb 2019 15:44:39 -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,
Nadav Amit <namit@...are.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>
Subject: [PATCH v3 08/20] x86/ftrace: Set trampoline pages as executable
From: Nadav Amit <namit@...are.com>
Since alloc_module() will not set the pages as executable soon, set
ftrace trampoline pages as executable after they are allocated.
For the time being, do not change ftrace to use the text_poke()
interface. As a result, ftrace still breaks W^X.
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Nadav Amit <namit@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
arch/x86/kernel/ftrace.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 8257a59704ae..13c8249b197f 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -742,6 +742,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
unsigned long end_offset;
unsigned long op_offset;
unsigned long offset;
+ unsigned long npages;
unsigned long size;
unsigned long retq;
unsigned long *ptr;
@@ -774,6 +775,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
return 0;
*tramp_size = size + RET_SIZE + sizeof(void *);
+ npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
/* Copy ftrace_caller onto the trampoline memory */
ret = probe_kernel_read(trampoline, (void *)start_offset, size);
@@ -818,6 +820,12 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
/* ALLOC_TRAMP flags lets us know we created it */
ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
+ /*
+ * Module allocation needs to be completed by making the page
+ * executable. The page is still writable, which is a security hazard,
+ * but anyhow ftrace breaks W^X completely.
+ */
+ set_memory_x((unsigned long)trampoline, npages);
return (unsigned long)trampoline;
fail:
tramp_free(trampoline, *tramp_size);
--
2.17.1
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