Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 05/48] mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done} | Date | Wed, 18 Jan 2017 11:46:14 +0100 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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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);
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