@@ -525,7 +525,7 @@ static int queue_pages_pte_range(pmd_t *
unsigned long flags = qp->flags;
int ret;
bool has_unmovable = false;
- pte_t *pte;
+ pte_t *pte, *mapped_pte;
spinlock_t *ptl;
ptl = pmd_trans_huge_lock(pmd, vma);
@@ -539,7 +539,7 @@ static int queue_pages_pte_range(pmd_t *
if (pmd_trans_unstable(pmd))
return 0;
- pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE) {
if (!pte_present(*pte))
continue;
@@ -571,7 +571,7 @@ static int queue_pages_pte_range(pmd_t *
} else
break;
}
- pte_unmap_unlock(pte - 1, ptl);
+ pte_unmap_unlock(mapped_pte, ptl);
cond_resched();
if (has_unmovable)
The patch titled Subject: mm: mempolicy: fix potential pte_unmap_unlock pte error has been added to the -mm tree. Its filename is mm-mempolicy-fix-potential-pte_unmap_unlock-pte-error.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-mempolicy-fix-potential-pte_unmap_unlock-pte-error.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-mempolicy-fix-potential-pte_unmap_unlock-pte-error.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Shijie Luo <luoshijie1@huawei.com> Subject: mm: mempolicy: fix potential pte_unmap_unlock pte error When flags in queue_pages_pte_range don't have MPOL_MF_MOVE or MPOL_MF_MOVE_ALL bits, code breaks and passing origin pte - 1 to pte_unmap_unlock seems like not a good idea. queue_pages_pte_range can run in MPOL_MF_MOVE_ALL mode which doesn't migrate misplaced pages but returns with EIO when encountering such a page. Since commit a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") and early break on the first pte in the range results in pte_unmap_unlock on an underflow pte. This can lead to lockups later on when somebody tries to lock the pte resp. page_table_lock again.. Link: https://lkml.kernel.org/r/20201019074853.50856-1-luoshijie1@huawei.com Fixes: a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") Signed-off-by: Shijie Luo <luoshijie1@huawei.com> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Feilong Lin <linfeilong@huawei.com> Cc: Shijie Luo <luoshijie1@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)