From 302b9e189962a94cde9770dacdacb4681e4524ba Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Tue, 11 Aug 2020 18:32:03 -0700 Subject: [PATCH] cma: don't quit at first error when activating reserved areas [ Upstream commit 3a5139f1c5bb76d69756fb8f13fffa173e261153 ] The routine cma_init_reserved_areas is designed to activate all reserved cma areas. It quits when it first encounters an error. This can leave some areas in a state where they are reserved but not activated. There is no feedback to code which performed the reservation. Attempting to allocate memory from areas in such a state will result in a BUG. Modify cma_init_reserved_areas to always attempt to activate all areas. The called routine, cma_activate_area is responsible for leaving the area in a valid state. No one is making active use of returned error codes, so change the routine to void. How to reproduce: This example uses kernelcore, hugetlb and cma as an easy way to reproduce. However, this is a more general cma issue. Two node x86 VM 16GB total, 8GB per node Kernel command line parameters, kernelcore=4G hugetlb_cma=8G Related boot time messages, hugetlb_cma: reserve 8192 MiB, up to 4096 MiB per node cma: Reserved 4096 MiB at 0x0000000100000000 hugetlb_cma: reserved 4096 MiB on node 0 cma: Reserved 4096 MiB at 0x0000000300000000 hugetlb_cma: reserved 4096 MiB on node 1 cma: CMA area hugetlb could not be activated # echo 8 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI ... Call Trace: bitmap_find_next_zero_area_off+0x51/0x90 cma_alloc+0x1a5/0x310 alloc_fresh_huge_page+0x78/0x1a0 alloc_pool_huge_page+0x6f/0xf0 set_max_huge_pages+0x10c/0x250 nr_hugepages_store_common+0x92/0x120 ? __kmalloc+0x171/0x270 kernfs_fop_write+0xc1/0x1a0 vfs_write+0xc7/0x1f0 ksys_write+0x5f/0xe0 do_syscall_64+0x4d/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator") Signed-off-by: Mike Kravetz Signed-off-by: Andrew Morton Reviewed-by: Roman Gushchin Acked-by: Barry Song Cc: Marek Szyprowski Cc: Michal Nazarewicz Cc: Kyungmin Park Cc: Joonsoo Kim Cc: Link: http://lkml.kernel.org/r/20200730163123.6451-1-mike.kravetz@oracle.com Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/cma.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/mm/cma.c b/mm/cma.c index be55d1988c67..7de520c0a1db 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -93,17 +93,15 @@ static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, mutex_unlock(&cma->lock); } -static int __init cma_activate_area(struct cma *cma) +static void __init cma_activate_area(struct cma *cma) { unsigned long base_pfn = cma->base_pfn, pfn = base_pfn; unsigned i = cma->count >> pageblock_order; struct zone *zone; cma->bitmap = bitmap_zalloc(cma_bitmap_maxno(cma), GFP_KERNEL); - if (!cma->bitmap) { - cma->count = 0; - return -ENOMEM; - } + if (!cma->bitmap) + goto out_error; WARN_ON_ONCE(!pfn_valid(pfn)); zone = page_zone(pfn_to_page(pfn)); @@ -133,25 +131,22 @@ static int __init cma_activate_area(struct cma *cma) spin_lock_init(&cma->mem_head_lock); #endif - return 0; + return; not_in_zone: - pr_err("CMA area %s could not be activated\n", cma->name); bitmap_free(cma->bitmap); +out_error: cma->count = 0; - return -EINVAL; + pr_err("CMA area %s could not be activated\n", cma->name); + return; } static int __init cma_init_reserved_areas(void) { int i; - for (i = 0; i < cma_area_count; i++) { - int ret = cma_activate_area(&cma_areas[i]); - - if (ret) - return ret; - } + for (i = 0; i < cma_area_count; i++) + cma_activate_area(&cma_areas[i]); return 0; }