| From: Miaohe Lin <linmiaohe@huawei.com> |
| Subject: mm/hugetlb: fix kernel NULL pointer dereference when migrating hugetlb folio |
| Date: Tue, 9 Jul 2024 20:04:33 +0800 |
| |
| A kernel crash was observed when migrating hugetlb folio: |
| |
| BUG: kernel NULL pointer dereference, address: 0000000000000008 |
| PGD 0 P4D 0 |
| Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI |
| CPU: 0 PID: 3435 Comm: bash Not tainted 6.10.0-rc6-00450-g8578ca01f21f #66 |
| RIP: 0010:__folio_undo_large_rmappable+0x70/0xb0 |
| RSP: 0018:ffffb165c98a7b38 EFLAGS: 00000097 |
| RAX: fffffbbc44528090 RBX: 0000000000000000 RCX: 0000000000000000 |
| RDX: ffffa30e000a2800 RSI: 0000000000000246 RDI: ffffa3153ffffcc0 |
| RBP: fffffbbc44528000 R08: 0000000000002371 R09: ffffffffbe4e5868 |
| R10: 0000000000000001 R11: 0000000000000001 R12: ffffa3153ffffcc0 |
| R13: fffffbbc44468000 R14: 0000000000000001 R15: 0000000000000001 |
| FS: 00007f5b3a716740(0000) GS:ffffa3151fc00000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 0000000000000008 CR3: 000000010959a000 CR4: 00000000000006f0 |
| Call Trace: |
| <TASK> |
| __folio_migrate_mapping+0x59e/0x950 |
| __migrate_folio.constprop.0+0x5f/0x120 |
| move_to_new_folio+0xfd/0x250 |
| migrate_pages+0x383/0xd70 |
| soft_offline_page+0x2ab/0x7f0 |
| soft_offline_page_store+0x52/0x90 |
| kernfs_fop_write_iter+0x12c/0x1d0 |
| vfs_write+0x380/0x540 |
| ksys_write+0x64/0xe0 |
| do_syscall_64+0xb9/0x1d0 |
| entry_SYSCALL_64_after_hwframe+0x77/0x7f |
| RIP: 0033:0x7f5b3a514887 |
| RSP: 002b:00007ffe138fce68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 |
| RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007f5b3a514887 |
| RDX: 000000000000000c RSI: 0000556ab809ee10 RDI: 0000000000000001 |
| RBP: 0000556ab809ee10 R08: 00007f5b3a5d1460 R09: 000000007fffffff |
| R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c |
| R13: 00007f5b3a61b780 R14: 00007f5b3a617600 R15: 00007f5b3a616a00 |
| |
| It's because hugetlb folio is passed to __folio_undo_large_rmappable() |
| unexpectedly. large_rmappable flag is imperceptibly set to hugetlb folio |
| since commit f6a8dd98a2ce ("hugetlb: convert alloc_buddy_hugetlb_folio to |
| use a folio"). Then commit be9581ea8c05 ("mm: fix crashes from deferred |
| split racing folio migration") makes folio_migrate_mapping() call |
| folio_undo_large_rmappable() triggering the bug. Fix this issue by |
| clearing large_rmappable flag for hugetlb folios. They don't need that |
| flag set anyway. |
| |
| Link: https://lkml.kernel.org/r/20240709120433.4136700-1-linmiaohe@huawei.com |
| Fixes: f6a8dd98a2ce ("hugetlb: convert alloc_buddy_hugetlb_folio to use a folio") |
| Fixes: be9581ea8c05 ("mm: fix crashes from deferred split racing folio migration") |
| Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> |
| Cc: Hugh Dickins <hughd@google.com> |
| Cc: Matthew Wilcox (Oracle) <willy@infradead.org> |
| Cc: Muchun Song <muchun.song@linux.dev> |
| Cc: <stable@vger.kernel.org> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/hugetlb.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/mm/hugetlb.c~mm-hugetlb-fix-kernel-null-pointer-dereference-when-migrating-hugetlb-folio |
| +++ a/mm/hugetlb.c |
| @@ -2166,6 +2166,9 @@ static struct folio *alloc_buddy_hugetlb |
| nid = numa_mem_id(); |
| retry: |
| folio = __folio_alloc(gfp_mask, order, nid, nmask); |
| + /* Ensure hugetlb folio won't have large_rmappable flag set. */ |
| + if (folio) |
| + folio_clear_large_rmappable(folio); |
| |
| if (folio && !folio_ref_freeze(folio, 1)) { |
| folio_put(folio); |
| _ |
