From: Andrew Morton <akpm@linux-foundation.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
Baoquan He <bhe@redhat.com>,
Sachin Sant <sachinp@linux.vnet.ibm.com>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
David Hildenbrand <david@redhat.com>,
Michal Hocko <mhocko@suse.com>,
Wei Yang <richardw.yang@linux.intel.com>,
Oscar Salvador <osalvador@suse.de>,
Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [PATCH] mm/sparse: Fix kernel crash with pfn_section_valid check
Date: Wed, 25 Mar 2020 17:38:17 -0700 [thread overview]
Message-ID: <20200325173817.a63f20dd0ec618e063569e4a@linux-foundation.org> (raw)
In-Reply-To: <20200325031914.107660-1-aneesh.kumar@linux.ibm.com>
On Wed, 25 Mar 2020 08:49:14 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:
> Fixes the below crash
(cc's added)
> BUG: Kernel NULL pointer dereference on read at 0x00000000
> Faulting instruction address: 0xc000000000c3447c
> Oops: Kernel access of bad area, sig: 11 [#1]
> LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> CPU: 11 PID: 7519 Comm: lt-ndctl Not tainted 5.6.0-rc7-autotest #1
> ...
> NIP [c000000000c3447c] vmemmap_populated+0x98/0xc0
> LR [c000000000088354] vmemmap_free+0x144/0x320
> Call Trace:
> section_deactivate+0x220/0x240
> __remove_pages+0x118/0x170
> arch_remove_memory+0x3c/0x150
> memunmap_pages+0x1cc/0x2f0
> devm_action_release+0x30/0x50
> release_nodes+0x2f8/0x3e0
> device_release_driver_internal+0x168/0x270
> unbind_store+0x130/0x170
> drv_attr_store+0x44/0x60
> sysfs_kf_write+0x68/0x80
> kernfs_fop_write+0x100/0x290
> __vfs_write+0x3c/0x70
> vfs_write+0xcc/0x240
> ksys_write+0x7c/0x140
> system_call+0x5c/0x68
>
> With commit: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case")
> section_mem_map is set to NULL after depopulate_section_mem(). This
> was done so that pfn_page() can work correctly with kernel config that disables
> SPARSEMEM_VMEMMAP. With that config pfn_to_page does
>
> __section_mem_map_addr(__sec) + __pfn;
> where
>
> static inline struct page *__section_mem_map_addr(struct mem_section *section)
> {
> unsigned long map = section->section_mem_map;
> map &= SECTION_MAP_MASK;
> return (struct page *)map;
> }
>
> Now with SPASEMEM_VMEMAP enabled, mem_section->usage->subsection_map is used to
> check the pfn validity (pfn_valid()). Since section_deactivate release
> mem_section->usage if a section is fully deactivated, pfn_valid() check after
> a subsection_deactivate cause a kernel crash.
>
> static inline int pfn_valid(unsigned long pfn)
> {
> ...
> return early_section(ms) || pfn_section_valid(ms, pfn);
> }
>
> where
>
> static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
> {
> int idx = subsection_map_index(pfn);
>
> return test_bit(idx, ms->usage->subsection_map);
> }
>
> Avoid this by clearing SECTION_HAS_MEM_MAP when mem_section->usage is freed.
>
> Fixes: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case")
d41e2f3bd546 had cc:stable, so I shall add cc:stable to this one as well.
> Cc: Baoquan He <bhe@redhat.com>
> Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
> mm/sparse.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index aadb7298dcef..3012d1f3771a 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -781,6 +781,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> ms->usage = NULL;
> }
> memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
> + /* Mark the section invalid */
> + ms->section_mem_map &= ~SECTION_HAS_MEM_MAP;
> }
>
> if (section_is_early && memmap)
next prev parent reply other threads:[~2020-03-26 0:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 3:19 [PATCH] mm/sparse: Fix kernel crash with pfn_section_valid check Aneesh Kumar K.V
2020-03-25 7:06 ` Baoquan He
2020-03-25 7:37 ` Baoquan He
2020-03-25 8:12 ` Aneesh Kumar K.V
2020-03-25 8:36 ` Baoquan He
2020-03-26 0:38 ` Andrew Morton [this message]
2020-03-26 9:40 ` Michal Hocko
2020-03-26 9:56 ` Aneesh Kumar K.V
2020-03-26 10:16 ` Michal Hocko
2020-03-26 10:50 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200325173817.a63f20dd0ec618e063569e4a@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=aneesh.kumar@linux.ibm.com \
--cc=bhe@redhat.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mhocko@suse.com \
--cc=mpe@ellerman.id.au \
--cc=osalvador@suse.de \
--cc=pankaj.gupta.linux@gmail.com \
--cc=richardw.yang@linux.intel.com \
--cc=rppt@linux.ibm.com \
--cc=sachinp@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).