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https://github.com/torvalds/linux
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mm/hugetlb: take page table lock in follow_huge_pmd()
We have a race condition between move_pages() and freeing hugepages, where
move_pages() calls follow_page(FOLL_GET) for hugepages internally and
tries to get its refcount without preventing concurrent freeing. This
race crashes the kernel, so this patch fixes it by moving FOLL_GET code
for hugepages into follow_huge_pmd() with taking the page table lock.
This patch intentionally removes page==NULL check after pte_page.
This is justified because pte_page() never returns NULL for any
architectures or configurations.
This patch changes the behavior of follow_huge_pmd() for tail pages and
then tail pages can be pinned/returned. So the caller must be changed to
properly handle the returned tail pages.
We could have a choice to add the similar locking to
follow_huge_(addr|pud) for consistency, but it's not necessary because
currently these functions don't support FOLL_GET flag, so let's leave it
for future development.
Here is the reproducer:
$ cat movepages.c
#include <stdio.h>
#include <stdlib.h>
#include <numaif.h>
#define ADDR_INPUT 0x700000000000UL
#define HPS 0x200000
#define PS 0x1000
int main(int argc, char *argv[]) {
int i;
int nr_hp = strtol(argv[1], NULL, 0);
int nr_p = nr_hp * HPS / PS;
int ret;
void **addrs;
int *status;
int *nodes;
pid_t pid;
pid = strtol(argv[2], NULL, 0);
addrs = malloc(sizeof(char *) * nr_p + 1);
status = malloc(sizeof(char *) * nr_p + 1);
nodes = malloc(sizeof(char *) * nr_p + 1);
while (1) {
for (i = 0; i < nr_p; i++) {
addrs[i] = (void *)ADDR_INPUT + i * PS;
nodes[i] = 1;
status[i] = 0;
}
ret = numa_move_pages(pid, nr_p, addrs, nodes, status,
MPOL_MF_MOVE_ALL);
if (ret == -1)
err("move_pages");
for (i = 0; i < nr_p; i++) {
addrs[i] = (void *)ADDR_INPUT + i * PS;
nodes[i] = 0;
status[i] = 0;
}
ret = numa_move_pages(pid, nr_p, addrs, nodes, status,
MPOL_MF_MOVE_ALL);
if (ret == -1)
err("move_pages");
}
return 0;
}
$ cat hugepage.c
#include <stdio.h>
#include <sys/mman.h>
#include <string.h>
#define ADDR_INPUT 0x700000000000UL
#define HPS 0x200000
int main(int argc, char *argv[]) {
int nr_hp = strtol(argv[1], NULL, 0);
char *p;
while (1) {
p = mmap((void *)ADDR_INPUT, nr_hp * HPS, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
if (p != (void *)ADDR_INPUT) {
perror("mmap");
break;
}
memset(p, 0, nr_hp * HPS);
munmap(p, nr_hp * HPS);
}
}
$ sysctl vm.nr_hugepages=40
$ ./hugepage 10 &
$ ./movepages 10 $(pgrep -f hugepage)
Fixes: e632a938d9
("mm: migrate: add hugepage migration code to move_pages()")
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Hugh Dickins <hughd@google.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: <stable@vger.kernel.org> [3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
cbef8478be
commit
e66f17ff71
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@ -99,9 +99,9 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep);
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struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
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int write);
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struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
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pmd_t *pmd, int write);
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pmd_t *pmd, int flags);
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struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
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pud_t *pud, int write);
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pud_t *pud, int flags);
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int pmd_huge(pmd_t pmd);
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int pud_huge(pud_t pmd);
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unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
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@ -133,8 +133,8 @@ static inline void hugetlb_report_meminfo(struct seq_file *m)
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static inline void hugetlb_show_meminfo(void)
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{
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}
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#define follow_huge_pmd(mm, addr, pmd, write) NULL
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#define follow_huge_pud(mm, addr, pud, write) NULL
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#define follow_huge_pmd(mm, addr, pmd, flags) NULL
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#define follow_huge_pud(mm, addr, pud, flags) NULL
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#define prepare_hugepage_range(file, addr, len) (-EINVAL)
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#define pmd_huge(x) 0
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#define pud_huge(x) 0
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@ -135,6 +135,8 @@ static inline void make_migration_entry_read(swp_entry_t *entry)
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*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
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}
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extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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spinlock_t *ptl);
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extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address);
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extern void migration_entry_wait_huge(struct vm_area_struct *vma,
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@ -148,6 +150,8 @@ static inline int is_migration_entry(swp_entry_t swp)
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}
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#define migration_entry_to_page(swp) NULL
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static inline void make_migration_entry_read(swp_entry_t *entryp) { }
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static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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spinlock_t *ptl) { }
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static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address) { }
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static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
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25
mm/gup.c
25
mm/gup.c
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@ -167,10 +167,10 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
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if (pud_none(*pud))
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return no_page_table(vma, flags);
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if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
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if (flags & FOLL_GET)
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return NULL;
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page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
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return page;
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page = follow_huge_pud(mm, address, pud, flags);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if (unlikely(pud_bad(*pud)))
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return no_page_table(vma, flags);
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@ -179,19 +179,10 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
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if (pmd_none(*pmd))
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return no_page_table(vma, flags);
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if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
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page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
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if (flags & FOLL_GET) {
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/*
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* Refcount on tail pages are not well-defined and
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* shouldn't be taken. The caller should handle a NULL
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* return when trying to follow tail pages.
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*/
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if (PageHead(page))
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get_page(page);
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else
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page = NULL;
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}
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return page;
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page = follow_huge_pmd(mm, address, pmd, flags);
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if (page)
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return page;
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return no_page_table(vma, flags);
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}
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if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
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return no_page_table(vma, flags);
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48
mm/hugetlb.c
48
mm/hugetlb.c
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@ -3675,28 +3675,48 @@ follow_huge_addr(struct mm_struct *mm, unsigned long address,
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struct page * __weak
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follow_huge_pmd(struct mm_struct *mm, unsigned long address,
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pmd_t *pmd, int write)
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pmd_t *pmd, int flags)
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{
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struct page *page;
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if (!pmd_present(*pmd))
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return NULL;
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page = pte_page(*(pte_t *)pmd);
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if (page)
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page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
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struct page *page = NULL;
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spinlock_t *ptl;
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retry:
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ptl = pmd_lockptr(mm, pmd);
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spin_lock(ptl);
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/*
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* make sure that the address range covered by this pmd is not
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* unmapped from other threads.
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*/
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if (!pmd_huge(*pmd))
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goto out;
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if (pmd_present(*pmd)) {
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page = pte_page(*(pte_t *)pmd) +
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((address & ~PMD_MASK) >> PAGE_SHIFT);
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if (flags & FOLL_GET)
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get_page(page);
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} else {
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if (is_hugetlb_entry_migration(huge_ptep_get((pte_t *)pmd))) {
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spin_unlock(ptl);
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__migration_entry_wait(mm, (pte_t *)pmd, ptl);
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goto retry;
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}
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/*
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* hwpoisoned entry is treated as no_page_table in
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* follow_page_mask().
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*/
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}
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out:
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spin_unlock(ptl);
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return page;
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}
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struct page * __weak
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follow_huge_pud(struct mm_struct *mm, unsigned long address,
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pud_t *pud, int write)
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pud_t *pud, int flags)
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{
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struct page *page;
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if (flags & FOLL_GET)
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return NULL;
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page = pte_page(*(pte_t *)pud);
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if (page)
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page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
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return page;
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return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
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}
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#ifdef CONFIG_MEMORY_FAILURE
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@ -197,7 +197,7 @@ static void remove_migration_ptes(struct page *old, struct page *new)
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* get to the page and wait until migration is finished.
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* When we return from this function the fault will be retried.
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*/
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static void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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spinlock_t *ptl)
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{
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pte_t pte;
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@ -1236,7 +1236,8 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
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goto put_and_set;
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if (PageHuge(page)) {
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isolate_huge_page(page, &pagelist);
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if (PageHead(page))
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isolate_huge_page(page, &pagelist);
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goto put_and_set;
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}
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