Commit 3c0dab44 authored Apr 25, 2019 by Nadav Amit Committed by Ingo Molnar Apr 30, 2019

x86/ftrace: Set trampoline pages as executable



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.

Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: <akpm@linux-foundation.org>
Cc: <ard.biesheuvel@linaro.org>
Cc: <deneen.t.dock@intel.com>
Cc: <kernel-hardening@lists.openwall.com>
Cc: <kristen@linux.intel.com>
Cc: <linux_dti@icloud.com>
Cc: <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190426001143.4983-10-namit@vmware.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 86a22057

arch/x86/kernel/ftrace.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -730,6 +730,7 @@ 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;
		@@ -762,6 +763,7 @@ 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);
		@@ -806,6 +808,12 @@ 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);