Messages in this thread Patch in this message | | | From | Rick Edgecombe <> | Subject | [PATCH v3 09/20] x86/kprobes: Set instruction page as executable | Date | Thu, 21 Feb 2019 15:44:40 -0800 |
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From: Nadav Amit <namit@vmware.com>
This patch is a preparatory patch for a following patch that makes module allocated pages non-executable. The patch sets the page as executable after allocation.
While at it, do some small cleanup of what appears to be unnecessary masking.
Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> --- 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 4ba75afba527..98c671e89889 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); } -- 2.17.1
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