| From eecc1e426d681351a6026a7d3e7d225f38955b6c Mon Sep 17 00:00:00 2001 |
| From: Hugh Dickins <hughd@google.com> |
| Date: Sun, 12 Jan 2014 01:25:21 -0800 |
| Subject: thp: fix copy_page_rep GPF by testing is_huge_zero_pmd once only |
| |
| From: Hugh Dickins <hughd@google.com> |
| |
| commit eecc1e426d681351a6026a7d3e7d225f38955b6c upstream. |
| |
| We see General Protection Fault on RSI in copy_page_rep: that RSI is |
| what you get from a NULL struct page pointer. |
| |
| RIP: 0010:[<ffffffff81154955>] [<ffffffff81154955>] copy_page_rep+0x5/0x10 |
| RSP: 0000:ffff880136e15c00 EFLAGS: 00010286 |
| RAX: ffff880000000000 RBX: ffff880136e14000 RCX: 0000000000000200 |
| RDX: 6db6db6db6db6db7 RSI: db73880000000000 RDI: ffff880dd0c00000 |
| RBP: ffff880136e15c18 R08: 0000000000000200 R09: 000000000005987c |
| R10: 000000000005987c R11: 0000000000000200 R12: 0000000000000001 |
| R13: ffffea00305aa000 R14: 0000000000000000 R15: 0000000000000000 |
| FS: 00007f195752f700(0000) GS:ffff880c7fc20000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 0000000093010000 CR3: 00000001458e1000 CR4: 00000000000027e0 |
| Call Trace: |
| copy_user_huge_page+0x93/0xab |
| do_huge_pmd_wp_page+0x710/0x815 |
| handle_mm_fault+0x15d8/0x1d70 |
| __do_page_fault+0x14d/0x840 |
| do_page_fault+0x2f/0x90 |
| page_fault+0x22/0x30 |
| |
| do_huge_pmd_wp_page() tests is_huge_zero_pmd(orig_pmd) four times: but |
| since shrink_huge_zero_page() can free the huge_zero_page, and we have |
| no hold of our own on it here (except where the fourth test holds |
| page_table_lock and has checked pmd_same), it's possible for it to |
| answer yes the first time, but no to the second or third test. Change |
| all those last three to tests for NULL page. |
| |
| (Note: this is not the same issue as trinity's DEBUG_PAGEALLOC BUG |
| in copy_page_rep with RSI: ffff88009c422000, reported by Sasha Levin |
| in https://lkml.org/lkml/2013/3/29/103. I believe that one is due |
| to the source page being split, and a tail page freed, while copy |
| is in progress; and not a problem without DEBUG_PAGEALLOC, since |
| the pmd_same check will prevent a miscopy from being made visible.) |
| |
| Fixes: 97ae17497e99 ("thp: implement refcounting for huge zero page") |
| Signed-off-by: Hugh Dickins <hughd@google.com> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| mm/huge_memory.c | 6 +++--- |
| 1 file changed, 3 insertions(+), 3 deletions(-) |
| |
| --- a/mm/huge_memory.c |
| +++ b/mm/huge_memory.c |
| @@ -1154,7 +1154,7 @@ alloc: |
| new_page = NULL; |
| |
| if (unlikely(!new_page)) { |
| - if (is_huge_zero_pmd(orig_pmd)) { |
| + if (!page) { |
| ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, |
| address, pmd, orig_pmd, haddr); |
| } else { |
| @@ -1181,7 +1181,7 @@ alloc: |
| |
| count_vm_event(THP_FAULT_ALLOC); |
| |
| - if (is_huge_zero_pmd(orig_pmd)) |
| + if (!page) |
| clear_huge_page(new_page, haddr, HPAGE_PMD_NR); |
| else |
| copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); |
| @@ -1207,7 +1207,7 @@ alloc: |
| page_add_new_anon_rmap(new_page, vma, haddr); |
| set_pmd_at(mm, haddr, pmd, entry); |
| update_mmu_cache_pmd(vma, address, pmd); |
| - if (is_huge_zero_pmd(orig_pmd)) { |
| + if (!page) { |
| add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); |
| put_huge_zero_page(); |
| } else { |