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Commit 7298e24f authored by Nadav Amit's avatar Nadav Amit Committed by Ingo Molnar
Browse files

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: default avatarNadav Amit <namit@vmware.com>
Signed-off-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.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/20190426001143.4983-11-namit@vmware.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3c0dab44

arch/x86/kernel/kprobes/core.c

+20 −4
Original line number Diff line number Diff line
@@ -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);

}