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authorAndrea Arcangeli <aarcange@redhat.com>2018-01-04 16:18:09 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-10 09:31:17 +0100
commit319122a71f306943a75217b3e78a9a0f8e9c1e95 (patch)
tree1e91265fcb42d3e6df3aefd6415b73ca6c69c083
parentc86ee796feed73dfa8a895be48c146b018d14393 (diff)
userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails
commit 0cbb4b4f4c44f54af268969b18d8deda63aded59 upstream. The previous fix in commit 384632e67e08 ("userfaultfd: non-cooperative: fix fork use after free") corrected the refcounting in case of UFFD_EVENT_FORK failure for the fork userfault paths. That still didn't clear the vma->vm_userfaultfd_ctx of the vmas that were set to point to the aborted new uffd ctx earlier in dup_userfaultfd. Link: http://lkml.kernel.org/r/20171223002505.593-2-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: syzbot <syzkaller@googlegroups.com> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Eric Biggers <ebiggers3@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/userfaultfd.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 1c713fd5b3e6..5aa392eae1c3 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -570,11 +570,14 @@ out:
static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
struct userfaultfd_wait_queue *ewq)
{
+ struct userfaultfd_ctx *release_new_ctx;
+
if (WARN_ON_ONCE(current->flags & PF_EXITING))
goto out;
ewq->ctx = ctx;
init_waitqueue_entry(&ewq->wq, current);
+ release_new_ctx = NULL;
spin_lock(&ctx->event_wqh.lock);
/*
@@ -601,8 +604,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
new = (struct userfaultfd_ctx *)
(unsigned long)
ewq->msg.arg.reserved.reserved1;
-
- userfaultfd_ctx_put(new);
+ release_new_ctx = new;
}
break;
}
@@ -617,6 +619,20 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
__set_current_state(TASK_RUNNING);
spin_unlock(&ctx->event_wqh.lock);
+ if (release_new_ctx) {
+ struct vm_area_struct *vma;
+ struct mm_struct *mm = release_new_ctx->mm;
+
+ /* the various vma->vm_userfaultfd_ctx still points to it */
+ down_write(&mm->mmap_sem);
+ 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;
+ up_write(&mm->mmap_sem);
+
+ userfaultfd_ctx_put(release_new_ctx);
+ }
+
/*
* ctx may go away after this if the userfault pseudo fd is
* already released.