Message-ID: <cad171ca-dc61-21d9-3a88-08fc85af6d73@de.bosch.com>
Date:   Mon, 4 Sep 2023 07:24:19 +0200
From:   "Behme Dirk (CM/ESO2)" <dirk.behme@...bosch.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     Dirk Behme <dirk.behme@...bosch.com>
Subject: Re: [PATCH 4.14 03/62] arm64: kprobe: make page to RO mode when
 allocate it


On 26.11.2018 11:50, Greg Kroah-Hartman wrote:
> 4.14-stable review patch.  If anyone has any objections, please let me know.


It looks like that this patch which was back ported from v4.20 to 
v4.14.100 needs the '__weak' on kernel/kprobes.c alloc_insn_page() from 
v4.15 commit

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=63fef14fc98a8b4fad7

to make alloc_insn_page() being used properly.

But that '__weak' from 63fef14fc98a8b4fad7 was not back ported to 
v4.14.x and is missing in v4.14.x ?

Best regards

Dirk


> ------------------
> 
> [ 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@...db.de>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Acked-by: Will Deacon <will.deacon@....com>
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> Reviewed-by: Laura Abbott <labbott@...hat.com>
> Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
> [catalin.marinas@....com: removed unnecessary casts]
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Sasha Levin <sashal@...nel.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 */

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