| From eb36ff41b3edd130a09114cde28bb18d60425c7b Mon Sep 17 00:00:00 2001 |
| From: Dan Williams <dan.j.williams@intel.com> |
| Date: Tue, 10 Jan 2017 16:57:36 -0800 |
| Subject: [PATCH] mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, |
| done} |
| |
| commit f931ab479dd24cf7a2c6e2df19778406892591fb upstream. |
| |
| Both arch_add_memory() and arch_remove_memory() expect a single threaded |
| context. |
| |
| For example, arch/x86/mm/init_64.c::kernel_physical_mapping_init() does |
| not hold any locks over this check and branch: |
| |
| if (pgd_val(*pgd)) { |
| pud = (pud_t *)pgd_page_vaddr(*pgd); |
| paddr_last = phys_pud_init(pud, __pa(vaddr), |
| __pa(vaddr_end), |
| page_size_mask); |
| continue; |
| } |
| |
| pud = alloc_low_page(); |
| paddr_last = phys_pud_init(pud, __pa(vaddr), __pa(vaddr_end), |
| page_size_mask); |
| |
| The result is that two threads calling devm_memremap_pages() |
| simultaneously can end up colliding on pgd initialization. This leads |
| to crash signatures like the following where the loser of the race |
| initializes the wrong pgd entry: |
| |
| BUG: unable to handle kernel paging request at ffff888ebfff0000 |
| IP: memcpy_erms+0x6/0x10 |
| PGD 2f8e8fc067 PUD 0 /* <---- Invalid PUD */ |
| Oops: 0000 [#1] SMP DEBUG_PAGEALLOC |
| CPU: 54 PID: 3818 Comm: systemd-udevd Not tainted 4.6.7+ #13 |
| task: ffff882fac290040 ti: ffff882f887a4000 task.ti: ffff882f887a4000 |
| RIP: memcpy_erms+0x6/0x10 |
| [..] |
| Call Trace: |
| ? pmem_do_bvec+0x205/0x370 [nd_pmem] |
| ? blk_queue_enter+0x3a/0x280 |
| pmem_rw_page+0x38/0x80 [nd_pmem] |
| bdev_read_page+0x84/0xb0 |
| |
| Hold the standard memory hotplug mutex over calls to |
| arch_{add,remove}_memory(). |
| |
| Fixes: 41e94a851304 ("add devm_memremap_pages") |
| Link: http://lkml.kernel.org/r/148357647831.9498.12606007370121652979.stgit@dwillia2-desk3.amr.corp.intel.com |
| Signed-off-by: Dan Williams <dan.j.williams@intel.com> |
| Cc: Christoph Hellwig <hch@lst.de> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/kernel/memremap.c b/kernel/memremap.c |
| index b501e390bb34..9ecedc28b928 100644 |
| --- a/kernel/memremap.c |
| +++ b/kernel/memremap.c |
| @@ -246,7 +246,9 @@ static void devm_memremap_pages_release(struct device *dev, void *data) |
| /* pages are dead and unused, undo the arch mapping */ |
| align_start = res->start & ~(SECTION_SIZE - 1); |
| align_size = ALIGN(resource_size(res), SECTION_SIZE); |
| + mem_hotplug_begin(); |
| arch_remove_memory(align_start, align_size); |
| + mem_hotplug_done(); |
| untrack_pfn(NULL, PHYS_PFN(align_start), align_size); |
| pgmap_radix_release(res); |
| dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc, |
| @@ -358,7 +360,9 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, |
| if (error) |
| goto err_pfn_remap; |
| |
| + mem_hotplug_begin(); |
| error = arch_add_memory(nid, align_start, align_size, true); |
| + mem_hotplug_done(); |
| if (error) |
| goto err_add_memory; |
| |
| -- |
| 2.10.1 |
| |