[PATCH v2 02/14] arm: adjust_pte() use pte_offset_map_rw_nolock()
From: Qi Zheng <hidden>
Date: 2024-08-22 07:14:00
Also in:
linux-arm-kernel, linux-mm, lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
In do_adjust_pte(), we may modify the pte entry. At this time, the write lock of mmap_lock is not held, and the pte_same() check is not performed after the PTL held. The corresponding pmd entry may have been modified concurrently. Therefore, in order to ensure the stability if pmd entry, use pte_offset_map_rw_nolock() to replace pte_offset_map_nolock(), and do pmd_same() check after holding the PTL. Signed-off-by: Qi Zheng <redacted> --- arch/arm/mm/fault-armv.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index 831793cd6ff94..de6c7d8a2ddfc 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c@@ -94,6 +94,7 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address, pud_t *pud; pmd_t *pmd; pte_t *pte; + pmd_t pmdval; int ret; pgd = pgd_offset(vma->vm_mm, address);
@@ -112,16 +113,22 @@ static int adjust_pte(struct vm_area_struct *vma, unsigned long address, if (pmd_none_or_clear_bad(pmd)) return 0; +again: /* * This is called while another page table is mapped, so we * must use the nested version. This also means we need to * open-code the spin-locking. */ - pte = pte_offset_map_nolock(vma->vm_mm, pmd, address, &ptl); + pte = pte_offset_map_rw_nolock(vma->vm_mm, pmd, address, &pmdval, &ptl); if (!pte) return 0; do_pte_lock(ptl); + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) { + do_pte_unlock(ptl); + pte_unmap(pte); + goto again; + } ret = do_adjust_pte(vma, address, pfn, pte);
--
2.20.1