* [PATCH] parisc: fix inability to allocate stack pages on exec
@ 2023-07-03 19:58 Mikulas Patocka
2023-07-03 20:06 ` Linus Torvalds
0 siblings, 1 reply; 4+ messages in thread
From: Mikulas Patocka @ 2023-07-03 19:58 UTC (permalink / raw)
To: Linus Torvalds
Cc: Vegard Nossum, John Paul Adrian Glaubitz, Frank Scheiner,
James E.J. Bottomley, Helge Deller, John David Anglin,
Andrew Morton, linux-parisc, linux-mm
Hi
The patch 8d7071af8907 ("mm: always expand the stack with the mmap write
lock held") breaks PA-RISC.
The breakage happens if we attempt to pass more arguments to execve than
what fits into the initial stack page - we get -E2BIG in such a case.
The reason for the breakage is that the commit 8d7071af8907 adds the test
"if (!(vma->vm_flags & VM_GROWSDOWN)) return -EFAULT;" to the function
expand_downwards.
expand_downwards is called from get_arg_page to allocate initial stack
pages. With the added test for VM_GROWSDOWN, it is not able to allocate
any pages on PA-RISC at all, and execve fails as soon as it tries to
allocate a stack page.
The bug can be fixed by dropping the test for VM_GROWSDOWN from
expand_downwards.
Fixes: 8d7071af8907 ("mm: always expand the stack with the mmap write lock held")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org # v6.4
---
mm/mmap.c | 3 ---
1 file changed, 3 deletions(-)
Index: linux-6.4.1/mm/mmap.c
===================================================================
--- linux-6.4.1.orig/mm/mmap.c 2023-07-03 18:17:35.000000000 +0200
+++ linux-6.4.1/mm/mmap.c 2023-07-03 21:22:44.000000000 +0200
@@ -2036,9 +2036,6 @@ int expand_downwards(struct vm_area_stru
struct vm_area_struct *prev;
int error = 0;
- if (!(vma->vm_flags & VM_GROWSDOWN))
- return -EFAULT;
-
address &= PAGE_MASK;
if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
return -EPERM;
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] parisc: fix inability to allocate stack pages on exec
2023-07-03 19:58 [PATCH] parisc: fix inability to allocate stack pages on exec Mikulas Patocka
@ 2023-07-03 20:06 ` Linus Torvalds
2023-07-03 20:40 ` Mikulas Patocka
0 siblings, 1 reply; 4+ messages in thread
From: Linus Torvalds @ 2023-07-03 20:06 UTC (permalink / raw)
To: Mikulas Patocka
Cc: Vegard Nossum, John Paul Adrian Glaubitz, Frank Scheiner,
James E.J. Bottomley, Helge Deller, John David Anglin,
Andrew Morton, linux-parisc, linux-mm
On Mon, 3 Jul 2023 at 12:59, Mikulas Patocka <mpatocka@redhat.com> wrote:
>
> The patch 8d7071af8907 ("mm: always expand the stack with the mmap write
> lock held") breaks PA-RISC.
>
> The breakage happens if we attempt to pass more arguments to execve than
> what fits into the initial stack page - we get -E2BIG in such a case.
>
> The reason for the breakage is that the commit 8d7071af8907 adds the test
> "if (!(vma->vm_flags & VM_GROWSDOWN)) return -EFAULT;" to the function
> expand_downwards.
Heh. See
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f66066bc5136f25e36a2daff4896c768f18c211e
which fixes this differently (and, I think, much better).
Just removing the VM_GROWSDOWN test will actually break some of the other users.
Notably the new and improved expand_stack() function that now handles
all the complicated *cough*ia64*cough* cases automatically, which
allowed unifying the page fault handling code around this area.
Linus
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] parisc: fix inability to allocate stack pages on exec
2023-07-03 20:06 ` Linus Torvalds
@ 2023-07-03 20:40 ` Mikulas Patocka
2023-07-03 20:42 ` Linus Torvalds
0 siblings, 1 reply; 4+ messages in thread
From: Mikulas Patocka @ 2023-07-03 20:40 UTC (permalink / raw)
To: Linus Torvalds
Cc: Vegard Nossum, John Paul Adrian Glaubitz, Frank Scheiner,
James E.J. Bottomley, Helge Deller, John David Anglin,
Andrew Morton, linux-parisc, linux-mm
On Mon, 3 Jul 2023, Linus Torvalds wrote:
> On Mon, 3 Jul 2023 at 12:59, Mikulas Patocka <mpatocka@redhat.com> wrote:
> >
> > The patch 8d7071af8907 ("mm: always expand the stack with the mmap write
> > lock held") breaks PA-RISC.
> >
> > The breakage happens if we attempt to pass more arguments to execve than
> > what fits into the initial stack page - we get -E2BIG in such a case.
> >
> > The reason for the breakage is that the commit 8d7071af8907 adds the test
> > "if (!(vma->vm_flags & VM_GROWSDOWN)) return -EFAULT;" to the function
> > expand_downwards.
>
> Heh. See
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f66066bc5136f25e36a2daff4896c768f18c211e
>
> which fixes this differently (and, I think, much better).
>
> Just removing the VM_GROWSDOWN test will actually break some of the other users.
>
> Notably the new and improved expand_stack() function that now handles
> all the complicated *cough*ia64*cough* cases automatically, which
> allowed unifying the page fault handling code around this area.
>
> Linus
Yes - I confirm that this fixes it.
(please, also send this patch to Greg, so that it will be included in
6.4.2)
Mikulas
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] parisc: fix inability to allocate stack pages on exec
2023-07-03 20:40 ` Mikulas Patocka
@ 2023-07-03 20:42 ` Linus Torvalds
0 siblings, 0 replies; 4+ messages in thread
From: Linus Torvalds @ 2023-07-03 20:42 UTC (permalink / raw)
To: Mikulas Patocka
Cc: Vegard Nossum, John Paul Adrian Glaubitz, Frank Scheiner,
James E.J. Bottomley, Helge Deller, John David Anglin,
Andrew Morton, linux-parisc, linux-mm
On Mon, 3 Jul 2023 at 13:40, Mikulas Patocka <mpatocka@redhat.com> wrote:
>
> (please, also send this patch to Greg, so that it will be included in
> 6.4.2)
Already part of the -rc1 review commits
https://lore.kernel.org/lkml/20230703184519.261119397@linuxfoundation.org/
Thanks,
Linus
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-07-03 19:58 [PATCH] parisc: fix inability to allocate stack pages on exec Mikulas Patocka
2023-07-03 20:06 ` Linus Torvalds
2023-07-03 20:40 ` Mikulas Patocka
2023-07-03 20:42 ` Linus Torvalds
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