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Date: Wed, 5 Jul 2017 00:51:05 +0300 (MSK)
From: Alexander Monakov <amonakov@...ras.ru>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] fix undefined behavior in ptrace
---
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:
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
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