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    Subject[PATCH 4.14 03/62] arm64: kprobe: make page to RO mode when allocate it
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 966866892cf89d606544bca22d584ba2ef9ec208 ]

    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()").

    Suggested-by: Arnd Bergmann <arnd@arndb.de>
    Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Acked-by: Will Deacon <will.deacon@arm.com>
    Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
    Reviewed-by: Laura Abbott <labbott@redhat.com>
    Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
    [catalin.marinas@arm.com: removed unnecessary casts]
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.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 22a5921562c7..0417c929d21a 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] = addr;
    + insns[0] = opcode;
    +
    + return aarch64_insn_patch_text(addrs, insns, 1);
    +}
    +
    static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
    {
    /* prepare insn slot */
    - p->ainsn.api.insn[0] = cpu_to_le32(p->opcode);
    + patch_text(p->ainsn.api.insn, p->opcode);

    flush_icache_range((uintptr_t) (p->ainsn.api.insn),
    (uintptr_t) (p->ainsn.api.insn) +
    @@ -118,15 +131,15 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
    return 0;
    }

    -static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
    +void *alloc_insn_page(void)
    {
    - void *addrs[1];
    - u32 insns[1];
    + void *page;

    - addrs[0] = (void *)addr;
    - insns[0] = (u32)opcode;
    + page = vmalloc_exec(PAGE_SIZE);
    + if (page)
    + set_memory_ro((unsigned long)page, 1);

    - return aarch64_insn_patch_text(addrs, insns, 1);
    + return page;
    }

    /* arm kprobe: install breakpoint in text */
    --
    2.17.1


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