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Message-ID: <20171108223555.52c01531@vmware.local.home>
Date: Wed, 8 Nov 2017 22:35:55 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Tobin C. Harding" <me@...in.cc>
Cc: kernel-hardening@...ts.openwall.com, "Jason A. Donenfeld"
<Jason@...c4.com>, Theodore Ts'o <tytso@....edu>, Linus Torvalds
<torvalds@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Paolo
Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts,
William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan
Glover <Golden_Miller83@...tonmail.ch>, Greg KH
<gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Joe Perches
<joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky
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<paulmck@...ux.vnet.ibm.com>, Andy Lutomirski <luto@...nel.org>, Peter
Zijlstra <peterz@...radead.org>, David Miller <davem@...emloft.net>,
Network Development <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kallsyms: don't leak address when printing symbol
On Thu, 9 Nov 2017 12:50:29 +1100
"Tobin C. Harding" <me@...in.cc> wrote:
> Currently if a pointer is printed using %p[ssB] and the symbol is not
> found (kallsyms_lookup() fails) then we print the actual address. This
> leaks kernel addresses. We should instead print something _safe_.
>
> Print "<no-symbol>" instead of kernel address.
Ug, ftrace requires this to work as is, as it uses it to print some
addresses that may or may not be a symbol.
If anything, can this return a success or failure if it were to find a
symbol or not, and then something like ftrace could decide to use %x if
it does not.
And yes, ftrace leaks kernel addresses all over the place, that's just
the nature of tracing the kernel.
-- Steve
>
> Signed-off-by: Tobin C. Harding <me@...in.cc>
> ---
> kernel/kallsyms.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 127e7cfafa55..182e7592be9c 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -390,7 +390,7 @@ static int __sprint_symbol(char *buffer, unsigned long address,
> address += symbol_offset;
> name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
> if (!name)
> - return sprintf(buffer, "0x%lx", address - symbol_offset);
> + return sprintf(buffer, "<no-symbol>");
>
> if (name != buffer)
> strcpy(buffer, name);
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