| From 542db12a9c42d1ce70c45091765e02f74c129f43 Mon Sep 17 00:00:00 2001 |
| From: Christophe Leroy <christophe.leroy@csgroup.eu> |
| Date: Mon, 31 Aug 2020 07:58:19 +0000 |
| Subject: powerpc: Fix random segfault when freeing hugetlb range |
| |
| From: Christophe Leroy <christophe.leroy@csgroup.eu> |
| |
| commit 542db12a9c42d1ce70c45091765e02f74c129f43 upstream. |
| |
| The following random segfault is observed from time to time with |
| map_hugetlb selftest: |
| |
| root@localhost:~# ./map_hugetlb 1 19 |
| 524288 kB hugepages |
| Mapping 1 Mbytes |
| Segmentation fault |
| |
| [ 31.219972] map_hugetlb[365]: segfault (11) at 117 nip 77974f8c lr 779a6834 code 1 in ld-2.23.so[77966000+21000] |
| [ 31.220192] map_hugetlb[365]: code: 9421ffc0 480318d1 93410028 90010044 9361002c 93810030 93a10034 93c10038 |
| [ 31.220307] map_hugetlb[365]: code: 93e1003c 93210024 8123007c 81430038 <80e90004> 814a0004 7f443a14 813a0004 |
| [ 31.221911] BUG: Bad rss-counter state mm:(ptrval) type:MM_FILEPAGES val:33 |
| [ 31.229362] BUG: Bad rss-counter state mm:(ptrval) type:MM_ANONPAGES val:5 |
| |
| This fault is due to hugetlb_free_pgd_range() freeing page tables |
| that are also used by regular pages. |
| |
| As explain in the comment at the beginning of |
| hugetlb_free_pgd_range(), the verification done in free_pgd_range() |
| on floor and ceiling is not done here, which means |
| hugetlb_free_pte_range() can free outside the expected range. |
| |
| As the verification cannot be done in hugetlb_free_pgd_range(), it |
| must be done in hugetlb_free_pte_range(). |
| |
| Fixes: b250c8c08c79 ("powerpc/8xx: Manage 512k huge pages as standard pages.") |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> |
| Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> |
| Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
| Link: https://lore.kernel.org/r/f0cb2a5477cd87d1eaadb128042e20aeb2bc2859.1598860677.git.christophe.leroy@csgroup.eu |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/powerpc/mm/hugetlbpage.c | 18 ++++++++++++++++-- |
| 1 file changed, 16 insertions(+), 2 deletions(-) |
| |
| --- a/arch/powerpc/mm/hugetlbpage.c |
| +++ b/arch/powerpc/mm/hugetlbpage.c |
| @@ -330,10 +330,24 @@ static void free_hugepd_range(struct mmu |
| get_hugepd_cache_index(pdshift - shift)); |
| } |
| |
| -static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd, unsigned long addr) |
| +static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd, |
| + unsigned long addr, unsigned long end, |
| + unsigned long floor, unsigned long ceiling) |
| { |
| + unsigned long start = addr; |
| pgtable_t token = pmd_pgtable(*pmd); |
| |
| + start &= PMD_MASK; |
| + if (start < floor) |
| + return; |
| + if (ceiling) { |
| + ceiling &= PMD_MASK; |
| + if (!ceiling) |
| + return; |
| + } |
| + if (end - 1 > ceiling - 1) |
| + return; |
| + |
| pmd_clear(pmd); |
| pte_free_tlb(tlb, token, addr); |
| mm_dec_nr_ptes(tlb->mm); |
| @@ -363,7 +377,7 @@ static void hugetlb_free_pmd_range(struc |
| */ |
| WARN_ON(!IS_ENABLED(CONFIG_PPC_8xx)); |
| |
| - hugetlb_free_pte_range(tlb, pmd, addr); |
| + hugetlb_free_pte_range(tlb, pmd, addr, end, floor, ceiling); |
| |
| continue; |
| } |