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Date: Wed, 3 Aug 2022 12:42:30 -0400
From: Rich Felker <dalias@...c.org>
To: Tudor Cretu <tudor.cretu@....com>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] clone: Return EINVAL for null stack
On Wed, Aug 03, 2022 at 03:42:48PM +0100, Tudor Cretu wrote:
>
>
> On 02-08-2022 19:53, Rich Felker wrote:
> >On Tue, Aug 02, 2022 at 12:30:36PM +0100, Tudor Cretu wrote:
> >>This change aligns the clone wrapper with the man page. If the stack is
> >>null, clone sets errno to EINVAL, instead of throwing a segmentation fault.
> >>---
> >> src/linux/clone.c | 5 +++++
> >> 1 file changed, 5 insertions(+)
> >>
> >>diff --git a/src/linux/clone.c b/src/linux/clone.c
> >>index 8c1af7d3..43a6803b 100644
> >>--- a/src/linux/clone.c
> >>+++ b/src/linux/clone.c
> >>@@ -1,4 +1,5 @@
> >> #define _GNU_SOURCE
> >>+#include <errno.h>
> >> #include <stdarg.h>
> >> #include <unistd.h>
> >> #include <sched.h>
> >>@@ -11,6 +12,10 @@ int clone(int (*func)(void *), void *stack, int flags, void *arg, ...)
> >> pid_t *ptid, *ctid;
> >> void *tls;
> >>+ if (!stack) {
> >>+ return __syscall_ret(-EINVAL);
> >>+ }
> >>+
> >> va_start(ap, arg);
> >> ptid = va_arg(ap, pid_t *);
> >> tls = va_arg(ap, void *);
> >>--
> >>2.25.1
> >
> >This is probably okay, but there's also a bigger discussion to be had
> >here about what to do about clone() -- deciding what the contract is
> >for what usage can be supported, and possibly making the rest produce
> >errors like the above. There's also a matter of the current very-wrong
> >use of va_arg for variadic arguments that might not exist, and which
> >probably *can't* exist in any valid application usage. This came up
> >before as part of the mt-fork work, but was basically deferred
> >indefinitely...
> >
> >Rich
>
> Hi Rich,
>
> Thank you for your reply. This is definitely a discussion to be had
> and I appreciate you sharing your thoughts. Just wanted to point out
> that the missing EINVAL issue popped up while running the LTP tests
> for clone. So, maybe this small change is still worth adding before
> having the bigger discussion.
Yeah, I'm inclined to agree.
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