From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org, akpm@linuxfoundation.org
Cc: linux-mm@kvack.org, Linux API <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Michal Hocko <mhocko@suse.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Minchan Kim <minchan@kernel.org>, Jann Horn <jannh@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Dave Hansen <dave.hansen@intel.com>,
Hugh Dickins <hughd@google.com>, Rik van Riel <riel@surriel.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>, Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Peter Xu <peterx@redhat.com>,
Rolf Eike Beer <eike-kernel@sf-tec.de>,
Ram Pai <linuxram@us.ibm.com>, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH v1] mm/madvise: report SIGBUS as -EFAULT for MADV_POPULATE_(READ|WRITE)
Date: Fri, 30 Jul 2021 14:23:51 +0200 [thread overview]
Message-ID: <dfd5ee42-0789-4373-4e1b-f6e902a80230@redhat.com> (raw)
In-Reply-To: <20210726154932.102880-1-david@redhat.com>
Hi Andrew,
sorry for not CCing you, absolutely no clue why I accidentally dropped
you. Can you give this patch a churn? It would be great if we could get
that into 5.14, so we don't have to deal with differing behavior between
Linux versions.
Cheers!
On 26.07.21 17:49, David Hildenbrand wrote:
> Doing some extended tests and polishing the man page update for
> MADV_POPULATE_(READ|WRITE), I realized that we end up converting also
> SIGBUS (via -EFAULT) to -EINVAL, making it look like yet another
> madvise() user error.
>
> We want to report only problematic mappings and permission problems that
> the user could have know as -EINVAL.
>
> Let's not convert -EFAULT arising due to SIGBUS (or SIGSEGV) to
> -EINVAL, but instead indicate -EFAULT to user space. While we could also
> convert it to -ENOMEM, using -EFAULT looks more helpful when user space
> might want to troubleshoot what's going wrong: MADV_POPULATE_(READ|WRITE)
> is not part of an final Linux release and we can still adjust the behavior.
>
> Fixes: 4ca9b3859dac ("mm/madvise: introduce MADV_POPULATE_(READ|WRITE) to prefault page tables")
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Jann Horn <jannh@google.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
> Cc: Matt Turner <mattst88@gmail.com>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Chris Zankel <chris@zankel.net>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
> Cc: Ram Pai <linuxram@us.ibm.com>
> Cc: Shuah Khan <shuah@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> mm/gup.c | 7 +++++--
> mm/madvise.c | 4 +++-
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 42b8b1fa6521..b94717977d17 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1558,9 +1558,12 @@ long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
> gup_flags |= FOLL_WRITE;
>
> /*
> - * See check_vma_flags(): Will return -EFAULT on incompatible mappings
> - * or with insufficient permissions.
> + * We want to report -EINVAL instead of -EFAULT for any permission
> + * problems or incompatible mappings.
> */
> + if (check_vma_flags(vma, gup_flags))
> + return -EINVAL;
> +
> return __get_user_pages(mm, start, nr_pages, gup_flags,
> NULL, NULL, locked);
> }
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 6d3d348b17f4..5c065bc8b5f6 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -862,10 +862,12 @@ static long madvise_populate(struct vm_area_struct *vma,
> switch (pages) {
> case -EINTR:
> return -EINTR;
> - case -EFAULT: /* Incompatible mappings / permissions. */
> + case -EINVAL: /* Incompatible mappings / permissions. */
> return -EINVAL;
> case -EHWPOISON:
> return -EHWPOISON;
> + case -EFAULT: /* VM_FAULT_SIGBUS or VM_FAULT_SIGSEGV */
> + return -EFAULT;
> default:
> pr_warn_once("%s: unhandled return value: %ld\n",
> __func__, pages);
>
--
Thanks,
David / dhildenb
prev parent reply other threads:[~2021-07-30 12:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 15:49 [PATCH v1] mm/madvise: report SIGBUS as -EFAULT for MADV_POPULATE_(READ|WRITE) David Hildenbrand
2021-07-30 12:23 ` David Hildenbrand [this message]
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