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Message-ID: <20170704215356.GT1627@brightrain.aerifal.cx>
Date: Tue, 4 Jul 2017 17:53:56 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] fix undefined behavior in ptrace
On Wed, Jul 05, 2017 at 12:51:05AM +0300, Alexander Monakov wrote:
> ---
> On Tue, 4 Jul 2017, Rich Felker wrote:
> > Thoughts?
>
> I'm not convinced it's a good idea, given that it's a Linux specific interface,
> and the manpage rather explicitly discourages passing fewer than four
> arguments.
>
> Plus, handling SPARC-specific differences of argument counts for
> PTRACE_{GET,SET}{FP,}REGS would be annoying.
>
> What makes sense is to retrieve the fifth argument only when needed:
Ah, okay. I'm fine with that. Thanks for clarifying.
> src/linux/ptrace.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/src/linux/ptrace.c b/src/linux/ptrace.c
> index 83b8022b..a3f393d9 100644
> --- a/src/linux/ptrace.c
> +++ b/src/linux/ptrace.c
> @@ -7,14 +7,18 @@ long ptrace(int req, ...)
> {
> va_list ap;
> pid_t pid;
> - void *addr, *data, *addr2;
> + void *addr, *data, *addr2 = 0;
> long ret, result;
>
> va_start(ap, req);
> pid = va_arg(ap, pid_t);
> addr = va_arg(ap, void *);
> data = va_arg(ap, void *);
> - addr2 = va_arg(ap, void *);
> + /* PTRACE_{READ,WRITE}{DATA,TEXT} (16...19) are specific to SPARC. */
> +#ifdef PTRACE_READDATA
> + if ((unsigned)req - PTRACE_READDATA < 4)
> + addr2 = va_arg(ap, void *);
> +#endif
> va_end(ap);
>
> if (req-1U < 3) data = &result;
> --
> 2.11.0
Applying.
Rich
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