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-rw-r--r--fs/proc/task_mmu.c18
-rw-r--r--fs/userfaultfd.c9
2 files changed, 27 insertions, 0 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 92a91e7816d8..95ca1fe7283c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1143,6 +1143,24 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
count = -EINTR;
goto out_mm;
}
+ /*
+ * Avoid to modify vma->vm_flags
+ * without locked ops while the
+ * coredump reads the vm_flags.
+ */
+ if (!mmget_still_valid(mm)) {
+ /*
+ * Silently return "count"
+ * like if get_task_mm()
+ * failed. FIXME: should this
+ * function have returned
+ * -ESRCH if get_task_mm()
+ * failed like if
+ * get_proc_task() fails?
+ */
+ up_write(&mm->mmap_sem);
+ goto out_mm;
+ }
for (vma = mm->mmap; vma; vma = vma->vm_next) {
vma->vm_flags &= ~VM_SOFTDIRTY;
vma_set_page_prot(vma);
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 89800fc7dc9d..f5de1e726356 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -629,6 +629,8 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
/* the various vma->vm_userfaultfd_ctx still points to it */
down_write(&mm->mmap_sem);
+ /* no task can run (and in turn coredump) yet */
+ VM_WARN_ON(!mmget_still_valid(mm));
for (vma = mm->mmap; vma; vma = vma->vm_next)
if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
@@ -883,6 +885,8 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
* taking the mmap_sem for writing.
*/
down_write(&mm->mmap_sem);
+ if (!mmget_still_valid(mm))
+ goto skip_mm;
prev = NULL;
for (vma = mm->mmap; vma; vma = vma->vm_next) {
cond_resched();
@@ -905,6 +909,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
vma->vm_flags = new_flags;
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
}
+skip_mm:
up_write(&mm->mmap_sem);
mmput(mm);
wakeup:
@@ -1333,6 +1338,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
goto out;
down_write(&mm->mmap_sem);
+ if (!mmget_still_valid(mm))
+ goto out_unlock;
vma = find_vma_prev(mm, start, &prev);
if (!vma)
goto out_unlock;
@@ -1520,6 +1527,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
goto out;
down_write(&mm->mmap_sem);
+ if (!mmget_still_valid(mm))
+ goto out_unlock;
vma = find_vma_prev(mm, start, &prev);
if (!vma)
goto out_unlock;