linux-kernel - Re: [PATCH RESEND] kprobes: be more permissive when user specifies both symbol name and address

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Message-ID: <CAHz2CGUEJ9at2dwj-H-phKrkxO_B3Xt-ksBa7ZsWb2bOZ2nY=g@mail.gmail.com>
Date:	Tue, 29 Jul 2014 20:50:08 +0800
From:	Jianyu Zhan <nasa4836@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Jianyu Zhan <nasa4836@...il.com>
Subject: Re: [PATCH RESEND] kprobes: be more permissive when user specifies
 both symbol name and address

Sorry for the noise,

plz add these Acked-by and Signed-off-by:

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Signed-off-by: Jianyu Zhan <nasa4836@...il.com>

Thanks,
Jianyu Zhan


On Tue, Jul 29, 2014 at 8:47 PM, Jianyu Zhan <nasa4836@...il.com> wrote:
> Hi, Ingo,
>
> Here is the new patch with typo fixed.
>
> Thanks.
>
> ---8<---
>
> Currently, if user specifies both symbol name and address, we just
> bail out.
>
> This might be too rude. This patch makes it give more tolerance.
> If both are specified, check address first, if the symbol found
> does not match the one user specify, print a waring. If not found,
> return -ENOENT, because some symbols might have muplitple instances,
> we don't bother to check symbol name.
> ---
>  Documentation/kprobes.txt |  4 +++-
>  kernel/kprobes.c          | 32 +++++++++++++++++++++++++++++---
>  2 files changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
> index 4bbeca8..663b5ad 100644
> --- a/Documentation/kprobes.txt
> +++ b/Documentation/kprobes.txt
> @@ -358,7 +358,9 @@ to install a probepoint is known. This field is used to calculate the
>  probepoint.
>
>  3. Specify either the kprobe "symbol_name" OR the "addr". If both are
> -specified, kprobe registration will fail with -EINVAL.
> +specified, only check "addr", because some symbols might have multiple
> +instances. If neither is specified, kprobe registration will fail
> +with -EINVAL.
>
>  4. With CISC architectures (such as i386 and x86_64), the kprobes code
>  does not validate if the kprobe.addr is at an instruction boundary.
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 734e9a7..9768608 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1358,15 +1358,41 @@ static bool within_kprobe_blacklist(unsigned long addr)
>  static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
>  {
>         kprobe_opcode_t *addr = p->addr;
> +       char namebuf[KSYM_NAME_LEN];
> +       const char *sym_name = NULL;
> +       unsigned long offset;
>
> -       if ((p->symbol_name && p->addr) ||
> -           (!p->symbol_name && !p->addr))
> +       if (!p->symbol_name && !p->addr)
>                 goto invalid;
>
> -       if (p->symbol_name) {
> +       /*
> +        * Some symbols might have multiple instances,
> +        * so if both are specified, only check address.
> +        */
> +       if (unlikely(p->addr && p->symbol_name)) {
> +               sym_name = kallsyms_lookup((unsigned long)(p->addr),
> +                               NULL, &offset, NULL, namebuf);
> +               if (!sym_name)
> +                       return ERR_PTR(-ENOENT);
> +
> +               if (strncmp(sym_name, p->symbol_name, KSYM_NAME_LEN)
> +                               || offset != p->offset) {
> +                       pr_err("Incorrect symbol or offset, should be "
> +                               "symbol=%s, offset=%ld.\n", sym_name, offset);
> +                       goto invalid;
> +               }
> +       } else if (p->symbol_name) {
> +               /* Only symbol case */
>                 kprobe_lookup_name(p->symbol_name, addr);
>                 if (!addr)
>                         return ERR_PTR(-ENOENT);
> +       } else {
> +               /*
> +                * Only address case.
> +                * Since we later will do a sanity check of the
> +                * address range in check_kprobe_address_safe(),
> +                * do nothing here.
> +                */
>         }
>
>         addr = (kprobe_opcode_t *)(((char *)addr) + p->offset);
> --
> 2.0.0
>
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