Commit 94395ad6 authored by Nadav Amit's avatar Nadav Amit Committed by Greg Kroah-Hartman

x86/kprobes: Set instruction page as executable

[ Upstream commit 7298e24f ]

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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 474ec2dc
......@@ -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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