BPF Archive on lore.kernel.org
 help / color / Atom feed
From: Masami Hiramatsu <mhiramat@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: x86@kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-parisc@vger.kernel.org, linux-um@lists.infradead.org,
	netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 14/23] tracing/kprobes: handle mixed kernel/userspace probes better
Date: Fri, 22 May 2020 09:04:50 +0900
Message-ID: <20200522090450.a6ef7a53878c61d10340949a@kernel.org> (raw)
In-Reply-To: <20200521152301.2587579-15-hch@lst.de>

On Thu, 21 May 2020 17:22:52 +0200
Christoph Hellwig <hch@lst.de> wrote:

> Instead of using the dangerous probe_kernel_read and strncpy_from_unsafe
> helpers, rework probes to try a user probe based on the address if the
> architecture has a common address space for kernel and userspace.
> 

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you!

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  kernel/trace/trace_kprobe.c | 72 ++++++++++++++++++++++---------------
>  1 file changed, 43 insertions(+), 29 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 4325f9e7fadaa..4aeaef53ba970 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1200,6 +1200,15 @@ static const struct file_operations kprobe_profile_ops = {
>  
>  /* Kprobe specific fetch functions */
>  
> +/* Return the length of string -- including null terminal byte */
> +static nokprobe_inline int
> +fetch_store_strlen_user(unsigned long addr)
> +{
> +	const void __user *uaddr =  (__force const void __user *)addr;
> +
> +	return strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
> +}
> +
>  /* Return the length of string -- including null terminal byte */
>  static nokprobe_inline int
>  fetch_store_strlen(unsigned long addr)
> @@ -1207,30 +1216,27 @@ fetch_store_strlen(unsigned long addr)
>  	int ret, len = 0;
>  	u8 c;
>  
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +	if (addr < TASK_SIZE)
> +		return fetch_store_strlen_user(addr);
> +#endif
> +
>  	do {
> -		ret = probe_kernel_read(&c, (u8 *)addr + len, 1);
> +		ret = probe_kernel_read_strict(&c, (u8 *)addr + len, 1);
>  		len++;
>  	} while (c && ret == 0 && len < MAX_STRING_SIZE);
>  
>  	return (ret < 0) ? ret : len;
>  }
>  
> -/* Return the length of string -- including null terminal byte */
> -static nokprobe_inline int
> -fetch_store_strlen_user(unsigned long addr)
> -{
> -	const void __user *uaddr =  (__force const void __user *)addr;
> -
> -	return strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
> -}
> -
>  /*
> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> - * length and relative data location.
> + * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> + * with max length and relative data location.
>   */
>  static nokprobe_inline int
> -fetch_store_string(unsigned long addr, void *dest, void *base)
> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
>  {
> +	const void __user *uaddr =  (__force const void __user *)addr;
>  	int maxlen = get_loc_len(*(u32 *)dest);
>  	void *__dest;
>  	long ret;
> @@ -1240,11 +1246,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
>  
>  	__dest = get_loc_data(dest, base);
>  
> -	/*
> -	 * Try to get string again, since the string can be changed while
> -	 * probing.
> -	 */
> -	ret = strncpy_from_unsafe(__dest, (void *)addr, maxlen);
> +	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
>  	if (ret >= 0)
>  		*(u32 *)dest = make_data_loc(ret, __dest - base);
>  
> @@ -1252,35 +1254,37 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
>  }
>  
>  /*
> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
> - * with max length and relative data location.
> + * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> + * length and relative data location.
>   */
>  static nokprobe_inline int
> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
> +fetch_store_string(unsigned long addr, void *dest, void *base)
>  {
> -	const void __user *uaddr =  (__force const void __user *)addr;
>  	int maxlen = get_loc_len(*(u32 *)dest);
>  	void *__dest;
>  	long ret;
>  
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +	if ((unsigned long)addr < TASK_SIZE)
> +		return fetch_store_string_user(addr, dest, base);
> +#endif
> +
>  	if (unlikely(!maxlen))
>  		return -ENOMEM;
>  
>  	__dest = get_loc_data(dest, base);
>  
> -	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
> +	/*
> +	 * Try to get string again, since the string can be changed while
> +	 * probing.
> +	 */
> +	ret = strncpy_from_user_nofault(__dest, (void *)addr, maxlen);
>  	if (ret >= 0)
>  		*(u32 *)dest = make_data_loc(ret, __dest - base);
>  
>  	return ret;
>  }
>  
> -static nokprobe_inline int
> -probe_mem_read(void *dest, void *src, size_t size)
> -{
> -	return probe_kernel_read(dest, src, size);
> -}
> -
>  static nokprobe_inline int
>  probe_mem_read_user(void *dest, void *src, size_t size)
>  {
> @@ -1289,6 +1293,16 @@ probe_mem_read_user(void *dest, void *src, size_t size)
>  	return probe_user_read(dest, uaddr, size);
>  }
>  
> +static nokprobe_inline int
> +probe_mem_read(void *dest, void *src, size_t size)
> +{
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +	if ((unsigned long)src < TASK_SIZE)
> +		return probe_mem_read_user(dest, src, size);
> +#endif
> +	return probe_kernel_read_strict(dest, src, size);
> +}
> +
>  /* Note that we don't verify it, since the code does not come from user space */
>  static int
>  process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
> -- 
> 2.26.2
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 15:22 clean up and streamline probe_kernel_* and friends v4 Christoph Hellwig
2020-05-21 15:22 ` [PATCH 01/23] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-21 15:22 ` [PATCH 02/23] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-21 15:22 ` [PATCH 03/23] maccess: remove duplicate kerneldoc comments Christoph Hellwig
2020-05-21 15:22 ` [PATCH 04/23] maccess: clarify " Christoph Hellwig
2020-05-21 15:22 ` [PATCH 05/23] maccess: update the top of file comment Christoph Hellwig
2020-05-21 15:22 ` [PATCH 06/23] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 07/23] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 08/23] maccess: rename strnlen_unsafe_user to strnlen_user_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 09/23] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-21 15:22 ` [PATCH 10/23] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-28  0:55   ` Andrew Morton
2020-05-21 15:22 ` [PATCH 11/23] bpf: factor out a bpf_trace_copy_string helper Christoph Hellwig
2020-05-21 22:10   ` Andrii Nakryiko
2020-05-21 15:22 ` [PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better Christoph Hellwig
2020-05-21 22:10   ` Andrii Nakryiko
2020-05-28  2:04   ` Andrew Morton
2020-05-28  2:26     ` Yonghong Song
2020-05-28  4:39       ` Christoph Hellwig
2020-05-28 17:06         ` Yonghong Song
2020-05-21 15:22 ` [PATCH 13/23] bpf: rework the compat kernel probe handling Christoph Hellwig
2020-05-21 22:10   ` Andrii Nakryiko
2020-05-21 15:22 ` [PATCH 14/23] tracing/kprobes: handle mixed kernel/userspace probes better Christoph Hellwig
2020-05-22  0:04   ` Masami Hiramatsu [this message]
2020-05-21 15:22 ` [PATCH 15/23] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-21 15:22 ` [PATCH 16/23] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-21 15:22 ` [PATCH 17/23] maccess: move user access routines together Christoph Hellwig
2020-05-21 15:22 ` [PATCH 18/23] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-21 15:22 ` [PATCH 19/23] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-21 15:22 ` [PATCH 20/23] maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 21/23] maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault Christoph Hellwig
2020-05-21 15:23 ` [PATCH 22/23] maccess: rename probe_kernel_address to get_kernel_nofault Christoph Hellwig
2020-05-21 15:23 ` [PATCH 23/23] maccess: return -ERANGE when copy_from_kernel_nofault_allowed fails Christoph Hellwig
2020-05-21 18:03 ` clean up and streamline probe_kernel_* and friends v4 Linus Torvalds
2020-05-22  0:22 ` Masami Hiramatsu
2020-05-25 22:19 ` Andrew Morton
2020-05-26  6:13   ` Christoph Hellwig
2020-05-28  0:36     ` Andrew Morton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200522090450.a6ef7a53878c61d10340949a@kernel.org \
    --to=mhiramat@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=hch@lst.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-um@lists.infradead.org \
    --cc=netdev@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

BPF Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/bpf/0 bpf/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 bpf bpf/ https://lore.kernel.org/bpf \
		bpf@vger.kernel.org
	public-inbox-index bpf

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.bpf


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git