* linux-next: Unable to write into a vma if it has been mapped without PROT_READ
@ 2016-02-29 19:11 ` Andrey Wagin
0 siblings, 0 replies; 5+ messages in thread
From: Andrey Wagin @ 2016-02-29 19:11 UTC (permalink / raw)
To: linux-next, linux-mm
Hello Everyone,
I found that now we can't write into a vma if it was mapped without PROT_READ:
mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
+++ killed by SIGSEGV (core dumped) +++
Segmentation fault
[root@linux-next-test ~]# cat test.c
#include <sys/mman.h>
#include <stdlib.h>
int main()
{
int *p;
p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
p[0] = 1;
return 0;
}
[root@linux-next-test ~]# uname -a
Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
This issue appeared in 4.5.0-rc5-next-20160226.
https://ci.openvz.org/job/CRIU-linux-next/152/console
Thanks,
Andrew
^ permalink raw reply [flat|nested] 5+ messages in thread* linux-next: Unable to write into a vma if it has been mapped without PROT_READ
@ 2016-02-29 19:11 ` Andrey Wagin
0 siblings, 0 replies; 5+ messages in thread
From: Andrey Wagin @ 2016-02-29 19:11 UTC (permalink / raw)
To: linux-next, linux-mm
Hello Everyone,
I found that now we can't write into a vma if it was mapped without PROT_READ:
mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
+++ killed by SIGSEGV (core dumped) +++
Segmentation fault
[root@linux-next-test ~]# cat test.c
#include <sys/mman.h>
#include <stdlib.h>
int main()
{
int *p;
p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
p[0] = 1;
return 0;
}
[root@linux-next-test ~]# uname -a
Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
This issue appeared in 4.5.0-rc5-next-20160226.
https://ci.openvz.org/job/CRIU-linux-next/152/console
Thanks,
Andrew
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: linux-next: Unable to write into a vma if it has been mapped without PROT_READ
2016-02-29 19:11 ` Andrey Wagin
@ 2016-02-29 20:15 ` Kirill A. Shutemov
-1 siblings, 0 replies; 5+ messages in thread
From: Kirill A. Shutemov @ 2016-02-29 20:15 UTC (permalink / raw)
To: Andrey Wagin, Dave Hansen; +Cc: linux-next, linux-mm
On Mon, Feb 29, 2016 at 11:11:37AM -0800, Andrey Wagin wrote:
> Hello Everyone,
>
> I found that now we can't write into a vma if it was mapped without PROT_READ:
>
> mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
> +++ killed by SIGSEGV (core dumped) +++
> Segmentation fault
> [root@linux-next-test ~]# cat test.c
> #include <sys/mman.h>
> #include <stdlib.h>
>
> int main()
> {
> int *p;
>
> p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> p[0] = 1;
>
> return 0;
> }
>
> [root@linux-next-test ~]# uname -a
> Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
> 17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>
> This issue appeared in 4.5.0-rc5-next-20160226.
>
> https://ci.openvz.org/job/CRIU-linux-next/152/console
Looks like the regression is caused by change in access_error() by commit
62b5f7d013fc ("mm/core, x86/mm/pkeys: Add execute-only protection keys support")
as per next-20160229.
/*
* Assume all accesses require either read or execute
* permissions. This is not an instruction access, so
* it requires read permissions.
*/
if (!(vma->vm_flags & VM_READ))
return 1;
The assumption is false, taking this testcase into account.
Dave?
--
Kirill A. Shutemov
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: linux-next: Unable to write into a vma if it has been mapped without PROT_READ
@ 2016-02-29 20:15 ` Kirill A. Shutemov
0 siblings, 0 replies; 5+ messages in thread
From: Kirill A. Shutemov @ 2016-02-29 20:15 UTC (permalink / raw)
To: Andrey Wagin, Dave Hansen; +Cc: linux-next, linux-mm
On Mon, Feb 29, 2016 at 11:11:37AM -0800, Andrey Wagin wrote:
> Hello Everyone,
>
> I found that now we can't write into a vma if it was mapped without PROT_READ:
>
> mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
> +++ killed by SIGSEGV (core dumped) +++
> Segmentation fault
> [root@linux-next-test ~]# cat test.c
> #include <sys/mman.h>
> #include <stdlib.h>
>
> int main()
> {
> int *p;
>
> p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> p[0] = 1;
>
> return 0;
> }
>
> [root@linux-next-test ~]# uname -a
> Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
> 17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>
> This issue appeared in 4.5.0-rc5-next-20160226.
>
> https://ci.openvz.org/job/CRIU-linux-next/152/console
Looks like the regression is caused by change in access_error() by commit
62b5f7d013fc ("mm/core, x86/mm/pkeys: Add execute-only protection keys support")
as per next-20160229.
/*
* Assume all accesses require either read or execute
* permissions. This is not an instruction access, so
* it requires read permissions.
*/
if (!(vma->vm_flags & VM_READ))
return 1;
The assumption is false, taking this testcase into account.
Dave?
--
Kirill A. Shutemov
--
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: linux-next: Unable to write into a vma if it has been mapped without PROT_READ
2016-02-29 20:15 ` Kirill A. Shutemov
(?)
@ 2016-03-01 1:00 ` Dave Hansen
-1 siblings, 0 replies; 5+ messages in thread
From: Dave Hansen @ 2016-03-01 1:00 UTC (permalink / raw)
To: Kirill A. Shutemov, Andrey Wagin; +Cc: linux-next, linux-mm
On 02/29/2016 12:15 PM, Kirill A. Shutemov wrote:
> On Mon, Feb 29, 2016 at 11:11:37AM -0800, Andrey Wagin wrote:
>> > Hello Everyone,
>> >
>> > I found that now we can't write into a vma if it was mapped without PROT_READ:
>> >
>> > mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
>> > --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
>> > +++ killed by SIGSEGV (core dumped) +++
>> > Segmentation fault
>> > [root@linux-next-test ~]# cat test.c
>> > #include <sys/mman.h>
>> > #include <stdlib.h>
>> >
>> > int main()
>> > {
>> > int *p;
>> >
>> > p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>> > p[0] = 1;
>> >
>> > return 0;
>> > }
>> >
>> > [root@linux-next-test ~]# uname -a
>> > Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
>> > 17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>> >
>> > This issue appeared in 4.5.0-rc5-next-20160226.
>> >
>> > https://ci.openvz.org/job/CRIU-linux-next/152/console
> Looks like the regression is caused by change in access_error() by commit
> 62b5f7d013fc ("mm/core, x86/mm/pkeys: Add execute-only protection keys support")
> as per next-20160229.
>
> /*
> * Assume all accesses require either read or execute
> * permissions. This is not an instruction access, so
> * it requires read permissions.
> */
> if (!(vma->vm_flags & VM_READ))
> return 1;
>
> The assumption is false, taking this testcase into account.
I'm taking a look at it. I might just be able to remove that check, but
I need to do a little due diligence with the execute-only support and
make sure I'm not breaking it.
Thanks for reporting this, btw!
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-02-29 19:11 linux-next: Unable to write into a vma if it has been mapped without PROT_READ Andrey Wagin
2016-02-29 19:11 ` Andrey Wagin
2016-02-29 20:15 ` Kirill A. Shutemov
2016-02-29 20:15 ` Kirill A. Shutemov
2016-03-01 1:00 ` Dave Hansen
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