On Tue, Oct 30, 2018 at 12:38:50PM +0100, Anders Roxell wrote:
> Commit 1404d6f13e47 ("arm64: dump: Add checking for writable and exectuable
> pages")
> has successfully identified code that leaves a page with W+X
> permissions.
>
> [ 3.245140] arm64/mm: Found insecure W+X mapping at address
> (____ptrval____)/0xffff000000d90000
> [ 3.245771] WARNING: CPU: 0 PID: 1 at ../arch/arm64/mm/dump.c:232
> note_page+0x410/0x420
> [ 3.246141] Modules linked in:
> [ 3.246653] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> 4.19.0-rc5-next-20180928-00001-ge70ae259b853-dirty #62
> [ 3.247008] Hardware name: linux,dummy-virt (DT)
> [ 3.247347] pstate: 80000005 (Nzcv daif -PAN -UAO)
> [ 3.247623] pc : note_page+0x410/0x420
> [ 3.247898] lr : note_page+0x410/0x420
> [ 3.248071] sp : ffff00000804bcd0
> [ 3.248254] x29: ffff00000804bcd0 x28: ffff000009274000
> [ 3.248578] x27: ffff00000921a000 x26: ffff80007dfff000
> [ 3.248845] x25: ffff0000093f5000 x24: ffff000009526f6a
> [ 3.249109] x23: 0000000000000004 x22: ffff000000d91000
> [ 3.249396] x21: ffff000000d90000 x20: 0000000000000000
> [ 3.249661] x19: ffff00000804bde8 x18: 0000000000000400
> [ 3.249924] x17: 0000000000000000 x16: 0000000000000000
> [ 3.250271] x15: ffffffffffffffff x14: 295f5f5f5f6c6176
> [ 3.250594] x13: 7274705f5f5f5f28 x12: 2073736572646461
> [ 3.250941] x11: 20746120676e6970 x10: 70616d20582b5720
> [ 3.251252] x9 : 6572756365736e69 x8 : 3039643030303030
> [ 3.251519] x7 : 306666666678302f x6 : ffff0000095467b2
> [ 3.251802] x5 : 0000000000000000 x4 : 0000000000000000
> [ 3.252060] x3 : 0000000000000000 x2 : ffffffffffffffff
> [ 3.252323] x1 : 4d151327adc50b00 x0 : 0000000000000000
> [ 3.252664] Call trace:
> [ 3.252953] note_page+0x410/0x420
> [ 3.253186] walk_pgd+0x12c/0x238
> [ 3.253417] ptdump_check_wx+0x68/0xf8
> [ 3.253637] mark_rodata_ro+0x68/0x98
> [ 3.253847] kernel_init+0x38/0x160
> [ 3.254103] ret_from_fork+0x10/0x18
>
> kprobes allocates a writable executable page with module_alloc() in
> order to store executable code.
> Reworked to that when allocate a page it sets mode RO. Inspired by
> commit 63fef14fc98a ("kprobes/x86: Make insn buffer always ROX and use
> text_poke()").
>
> Cc: Laura Abbott <labb...@redhat.com>
> Cc: Catalin Marinas <catalin.mari...@arm.com>
> Co-developed-by: Arnd Bergmann <a...@arndb.de>
> Co-developed-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
> Signed-off-by: Anders Roxell <anders.rox...@linaro.org>
> ---
> arch/arm64/kernel/probes/kprobes.c | 27 ++++++++++++++++++++-------
> 1 file changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kernel/probes/kprobes.c
> b/arch/arm64/kernel/probes/kprobes.c
> index 9b65132e789a..decf483b4153 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -23,7 +23,9 @@
> #include <linux/slab.h>
> #include <linux/stop_machine.h>
> #include <linux/sched/debug.h>
> +#include <linux/set_memory.h>
> #include <linux/stringify.h>
> +#include <linux/vmalloc.h>
> #include <asm/traps.h>
> #include <asm/ptrace.h>
> #include <asm/cacheflush.h>
> @@ -42,10 +44,21 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> static void __kprobes
> post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
>
> +static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
> +{
> + void *addrs[1];
> + u32 insns[1];
> +
> + addrs[0] = (void *)addr;
> + insns[0] = (u32)opcode;
I know they exist already, but I think you can drop these casts (Catalin can
do it when he picks this up -- no need to respin).
With that:
Acked-by: Will Deacon <will.dea...@arm.com>
Thanks for respinning so quickly.
Will
