[ Upstream commit 7298e24f904224fa79eb8fd7e0fbd78950ccf2db ] 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 <na...@vmware.com> Signed-off-by: Rick Edgecombe <rick.p.edgeco...@intel.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: <a...@linux-foundation.org> Cc: <ard.biesheu...@linaro.org> Cc: <deneen.t.d...@intel.com> Cc: <kernel-harden...@lists.openwall.com> Cc: <kris...@linux.intel.com> Cc: <linux_...@icloud.com> Cc: <will.dea...@arm.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Rik van Riel <r...@surriel.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: https://lkml.kernel.org/r/20190426001143.4983-11-na...@vmware.com Signed-off-by: Ingo Molnar <mi...@kernel.org> Signed-off-by: Sasha Levin <sas...@kernel.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 544bc2dfe408..e83a057564d1 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); } -- 2.20.1
