From: Nadav Amit namit@vmware.com
[ Upstream commit 3c0dab44e22782359a0a706cbce72de99a22aa75 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/ftrace.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 763d4264d16a6..aebec0b91d746 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -729,6 +729,7 @@ 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; @@ -761,6 +762,7 @@ 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); @@ -805,6 +807,12 @@ 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);