diff options
| -rw-r--r-- | include/linux/mm_types.h | 15 | ||||
| -rw-r--r-- | mm/memory.c | 14 |
2 files changed, 23 insertions, 6 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 165c58b12ccc..003619fab20e 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -660,6 +660,9 @@ struct vma_numab_state { * per VM-area/task. A VM area is any part of the process virtual memory * space that has a special rule for the page-fault handlers (ie a shared * library, the executable area etc). + * + * Only explicitly marked struct members may be accessed by RCU readers before + * getting a stable reference. */ struct vm_area_struct { /* The first cache line has the info for VMA tree walking. */ @@ -675,7 +678,11 @@ struct vm_area_struct { #endif }; - struct mm_struct *vm_mm; /* The address space we belong to. */ + /* + * The address space we belong to. + * Unstable RCU readers are allowed to read this. + */ + struct mm_struct *vm_mm; pgprot_t vm_page_prot; /* Access permissions of this VMA. */ /* @@ -688,7 +695,10 @@ struct vm_area_struct { }; #ifdef CONFIG_PER_VMA_LOCK - /* Flag to indicate areas detached from the mm->mm_mt tree */ + /* + * Flag to indicate areas detached from the mm->mm_mt tree. + * Unstable RCU readers are allowed to read this. + */ bool detached; /* @@ -706,6 +716,7 @@ struct vm_area_struct { * slowpath. */ int vm_lock_seq; + /* Unstable RCU readers are allowed to read this. */ struct vma_lock *vm_lock; #endif diff --git a/mm/memory.c b/mm/memory.c index 661168a46b43..46a44dc702fa 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5997,10 +5997,6 @@ retry: if (!vma_start_read(vma)) goto inval; - /* Check since vm_start/vm_end might change before we lock the VMA */ - if (unlikely(address < vma->vm_start || address >= vma->vm_end)) - goto inval_end_read; - /* Check if the VMA got isolated after we found it */ if (vma->detached) { vma_end_read(vma); @@ -6008,6 +6004,16 @@ retry: /* The area was replaced with another one */ goto retry; } + /* + * At this point, we have a stable reference to a VMA: The VMA is + * locked and we know it hasn't already been isolated. + * From here on, we can access the VMA without worrying about which + * fields are accessible for RCU readers. + */ + + /* Check since vm_start/vm_end might change before we lock the VMA */ + if (unlikely(address < vma->vm_start || address >= vma->vm_end)) + goto inval_end_read; rcu_read_unlock(); return vma; |