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/f0cb2a5477cd87d1eaadb128042e20aeb2bc2859.159886067... 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; }