[ 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@xxxxxxxxxx> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Cc: <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: <ard.biesheuvel@xxxxxxxxxx> Cc: <deneen.t.dock@xxxxxxxxx> Cc: <kernel-hardening@xxxxxxxxxxxxxxxxxx> Cc: <kristen@xxxxxxxxxxxxxxx> Cc: <linux_dti@xxxxxxxxxx> Cc: <will.deacon@xxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20190426001143.4983-10-namit@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 bd553b3af22e9..6e0c0ed8e4bf4 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -749,6 +749,7 @@ 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; @@ -781,6 +782,7 @@ 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); @@ -825,6 +827,12 @@ 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); -- 2.20.1
