| From f931ab479dd24cf7a2c6e2df19778406892591fb 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: mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done} |
| |
| From: Dan Williams <dan.j.williams@intel.com> |
| |
| 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> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| kernel/memremap.c | 4 ++++ |
| 1 file changed, 4 insertions(+) |
| |
| --- a/kernel/memremap.c |
| +++ b/kernel/memremap.c |
| @@ -159,7 +159,9 @@ static void devm_memremap_pages_release( |
| struct page_map *page_map = res; |
| |
| /* pages are dead and unused, undo the arch mapping */ |
| + mem_hotplug_begin(); |
| arch_remove_memory(page_map->res.start, resource_size(&page_map->res)); |
| + mem_hotplug_done(); |
| } |
| |
| void *devm_memremap_pages(struct device *dev, struct resource *res) |
| @@ -189,7 +191,9 @@ void *devm_memremap_pages(struct device |
| if (nid < 0) |
| nid = numa_mem_id(); |
| |
| + mem_hotplug_begin(); |
| error = arch_add_memory(nid, res->start, resource_size(res), true); |
| + mem_hotplug_done(); |
| if (error) { |
| devres_free(page_map); |
| return ERR_PTR(error); |