* [PATCH 0/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
@ 2018-12-06 21:20 Andrea Arcangeli
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
0 siblings, 1 reply; 5+ messages in thread
From: Andrea Arcangeli @ 2018-12-06 21:20 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Hugh Dickins, Mike Rapoport,
Mike Kravetz, Jann Horn, Peter Xu, Dr. David Alan Gilbert
Hello,
The juxtaposition with the other bugchecks didn't make it apparent
that the this WARN_ON was one line too soon.
An app trying to unregister a not-yet-registered range will trigger an
_harmless_ false positive WARN_ON. No real app would do that so it
went unnoticed during testing.
This should be applied on top of 29ec90660d68 ("userfaultfd:
shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas") to shut off
the false positive warning.
Thanks,
Andrea
Andrea Arcangeli (1):
userfaultfd: check VM_MAYWRITE was set after verifying the uffd is
registered
fs/userfaultfd.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
2018-12-06 21:20 [PATCH 0/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Andrea Arcangeli
@ 2018-12-06 21:20 ` Andrea Arcangeli
2018-12-06 21:32 ` Mike Rapoport
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Andrea Arcangeli @ 2018-12-06 21:20 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Hugh Dickins, Mike Rapoport,
Mike Kravetz, Jann Horn, Peter Xu, Dr. David Alan Gilbert
Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd
could trigger an harmless false positive WARN_ON. Check the vma is
already registered before checking VM_MAYWRITE to shut off the
false positive warning.
Cc: <stable@vger.kernel.org>
Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
fs/userfaultfd.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index cd58939dc977..7a85e609fc27 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
cond_resched();
BUG_ON(!vma_can_userfault(vma));
- WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
/*
* Nothing to do: this vma is already registered into this
@@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
if (!vma->vm_userfaultfd_ctx.ctx)
goto skip;
+ WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
+
if (vma->vm_start > start)
start = vma->vm_start;
vma_end = min(end, vma->vm_end);
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
@ 2018-12-06 21:32 ` Mike Rapoport
2018-12-06 22:07 ` Hugh Dickins
2018-12-07 3:43 ` Peter Xu
2 siblings, 0 replies; 5+ messages in thread
From: Mike Rapoport @ 2018-12-06 21:32 UTC (permalink / raw)
To: Andrea Arcangeli
Cc: Andrew Morton, linux-mm, linux-kernel, Hugh Dickins,
Mike Rapoport, Mike Kravetz, Jann Horn, Peter Xu,
Dr. David Alan Gilbert
On Thu, Dec 06, 2018 at 04:20:28PM -0500, Andrea Arcangeli wrote:
> Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd
> could trigger an harmless false positive WARN_ON. Check the vma is
> already registered before checking VM_MAYWRITE to shut off the
> false positive warning.
>
> Cc: <stable@vger.kernel.org>
> Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
> Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
> fs/userfaultfd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..7a85e609fc27 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> cond_resched();
>
> BUG_ON(!vma_can_userfault(vma));
> - WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
>
> /*
> * Nothing to do: this vma is already registered into this
> @@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> if (!vma->vm_userfaultfd_ctx.ctx)
> goto skip;
>
> + WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
> +
> if (vma->vm_start > start)
> start = vma->vm_start;
> vma_end = min(end, vma->vm_end);
>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
2018-12-06 21:32 ` Mike Rapoport
@ 2018-12-06 22:07 ` Hugh Dickins
2018-12-07 3:43 ` Peter Xu
2 siblings, 0 replies; 5+ messages in thread
From: Hugh Dickins @ 2018-12-06 22:07 UTC (permalink / raw)
To: Andrea Arcangeli
Cc: Andrew Morton, linux-mm, linux-kernel, Hugh Dickins,
Mike Rapoport, Mike Kravetz, Jann Horn, Peter Xu,
Dr. David Alan Gilbert
On Thu, 6 Dec 2018, Andrea Arcangeli wrote:
> Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd
> could trigger an harmless false positive WARN_ON. Check the vma is
> already registered before checking VM_MAYWRITE to shut off the
> false positive warning.
>
> Cc: <stable@vger.kernel.org>
> Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
> Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
> ---
> fs/userfaultfd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..7a85e609fc27 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> cond_resched();
>
> BUG_ON(!vma_can_userfault(vma));
> - WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
>
> /*
> * Nothing to do: this vma is already registered into this
> @@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> if (!vma->vm_userfaultfd_ctx.ctx)
> goto skip;
>
> + WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
> +
> if (vma->vm_start > start)
> start = vma->vm_start;
> vma_end = min(end, vma->vm_end);
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
2018-12-06 21:32 ` Mike Rapoport
2018-12-06 22:07 ` Hugh Dickins
@ 2018-12-07 3:43 ` Peter Xu
2 siblings, 0 replies; 5+ messages in thread
From: Peter Xu @ 2018-12-07 3:43 UTC (permalink / raw)
To: Andrea Arcangeli
Cc: Andrew Morton, linux-mm, linux-kernel, Hugh Dickins,
Mike Rapoport, Mike Kravetz, Jann Horn, Dr. David Alan Gilbert
On Thu, Dec 06, 2018 at 04:20:28PM -0500, Andrea Arcangeli wrote:
> Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd
> could trigger an harmless false positive WARN_ON. Check the vma is
> already registered before checking VM_MAYWRITE to shut off the
> false positive warning.
>
> Cc: <stable@vger.kernel.org>
> Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas")
> Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
> fs/userfaultfd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..7a85e609fc27 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> cond_resched();
>
> BUG_ON(!vma_can_userfault(vma));
> - WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
>
> /*
> * Nothing to do: this vma is already registered into this
Maybe we want to fix this comment too some day:
/*
* Nothing to do: this vma is already registered into this
* userfaultfd and with the right tracking mode too.
*/
But I don't think it's anything urgent since it's clear it means the
other way round and it can potentially be touched up in any further
cleanup/fixes of uffd.
Acked-by: Peter Xu <peterx@redhat.com>
> @@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> if (!vma->vm_userfaultfd_ctx.ctx)
> goto skip;
>
> + WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
> +
> if (vma->vm_start > start)
> start = vma->vm_start;
> vma_end = min(end, vma->vm_end);
Thanks,
--
Peter Xu
^ permalink raw reply [flat|nested] 5+ messages in thread
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2018-12-06 21:20 [PATCH 0/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Andrea Arcangeli
2018-12-06 21:20 ` [PATCH 1/1] " Andrea Arcangeli
2018-12-06 21:32 ` Mike Rapoport
2018-12-06 22:07 ` Hugh Dickins
2018-12-07 3:43 ` Peter Xu
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