[v2] clone.2: note EINVAL when exit_signal + bad flags
Checks
Commit Message
Document that Linux will report EINVAL when exit_signal is specified and
either CLONE_THREAD or CLONE_PARENT is specified.
From clone3_args_valid in Linux:
```
if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
kargs->exit_signal)
return false;
```
I have verified that this happens on my kernel with a small program:
```
#include <stdio.h>
#include <linux/sched.h>
#include <signal.h>
#include <sys/syscall.h>
#include <unistd.h>
int main() {
struct clone_args ca = {
.flags = CLONE_THREAD | CLONE_SIGHAND | CLONE_VM,
.exit_signal = SIGCHLD, // comment me out to fix error
.set_tid_size = 0,
};
syscall(SYS_clone3, &ca, sizeof(struct clone_args));
perror("");
}
```
And I have verified that this doesn't happen with normal `clone` through
the glibc helper:
```
#define _GNU_SOURCE
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
int do_nothing(void *_) { return 0; }
int main() {
void *map = mmap(NULL, 0x10000, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
void *stack_top = map + 0x10000 - 1;
clone(do_nothing, stack_top,
CLONE_THREAD | CLONE_VM | CLONE_SIGHAND | SIGCHLD, NULL);
perror("");
}
```
Signed-off-by: Jack Pearson <jack@pearson.onl>
---
man2/clone.2 | 10 ++++++++++
1 file changed, 10 insertions(+)
Comments
Hello,
In this patch, I included my test program for the absence of this behavior with
normal `clone` per Alex's request:
https://lore.kernel.org/linux-man/fba3de52-91cc-6cbe-b4ae-7140564e9ad2@pearson.onl/T/#mde63a642e9c8d0b4e367b0a2817248e8e0b29a50
Let me know if there's anything else I should do.
Thanks,
Jack
On 12/14/22 13:28, Jack Pearson wrote:
> Document that Linux will report EINVAL when exit_signal is specified and
> either CLONE_THREAD or CLONE_PARENT is specified.
>
...
Hi Jack,
On 2/22/23 03:28, Jack Pearson wrote:
> Hello,
>
> In this patch, I included my test program for the absence of this
> behavior with
> normal `clone` per Alex's request:
>
> https://lore.kernel.org/linux-man/fba3de52-91cc-6cbe-b4ae-7140564e9ad2@pearson.onl/T/#mde63a642e9c8d0b4e367b0a2817248e8e0b29a50
>
> Let me know if there's anything else I should do.
Could you please resend the patch (keeping all CCs), and I'll have a
look at it again?
Thanks for the ping,
Alex
>
> Thanks,
> Jack
>
> On 12/14/22 13:28, Jack Pearson wrote:
>> Document that Linux will report EINVAL when exit_signal is specified and
>> either CLONE_THREAD or CLONE_PARENT is specified.
>>
> ...
--
<http://www.alejandro-colomar.es/>
GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5
Alright, done!
Thanks,
Jack
On 2/24/23 17:04, Alex Colomar wrote:
> Hi Jack,
>
> On 2/22/23 03:28, Jack Pearson wrote:
>> Hello,
>>
>> In this patch, I included my test program for the absence of this behavior with
>> normal `clone` per Alex's request:
>>
>> https://lore.kernel.org/linux-man/fba3de52-91cc-6cbe-b4ae-7140564e9ad2@pearson.onl/T/#mde63a642e9c8d0b4e367b0a2817248e8e0b29a50
>>
>> Let me know if there's anything else I should do.
>
> Could you please resend the patch (keeping all CCs), and I'll have a look at it again?
>
> Thanks for the ping,
>
> Alex
>
>>
>> Thanks,
>> Jack
>>
>> On 12/14/22 13:28, Jack Pearson wrote:
>>> Document that Linux will report EINVAL when exit_signal is specified and
>>> either CLONE_THREAD or CLONE_PARENT is specified.
>>>
>> ...
>
@@ -1435,6 +1435,16 @@ One of the PIDs specified in
.I set_tid
was an invalid.
.TP
+.BR EINVAL " (" clone3 "() only)"
+.\" commit 7f192e3cd316ba58c88dfa26796cf77789dd9872
+.B CLONE_THREAD
+or
+.B CLONE_PARENT
+was specified in the
+.I flags
+mask, but a signal was specified in
+.I exit_signal.
+.TP
.BR EINVAL " (AArch64 only, Linux 4.6 and earlier)"
.I stack
was not aligned to a 128-bit boundary.