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userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails
The previous fix in commit 384632e67e
("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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
d09cfbbfa0
commit
0cbb4b4f4c
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@ -570,11 +570,14 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
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static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
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struct userfaultfd_wait_queue *ewq)
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{
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struct userfaultfd_ctx *release_new_ctx;
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if (WARN_ON_ONCE(current->flags & PF_EXITING))
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goto out;
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ewq->ctx = ctx;
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init_waitqueue_entry(&ewq->wq, current);
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release_new_ctx = NULL;
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spin_lock(&ctx->event_wqh.lock);
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/*
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@ -601,8 +604,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
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new = (struct userfaultfd_ctx *)
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(unsigned long)
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ewq->msg.arg.reserved.reserved1;
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userfaultfd_ctx_put(new);
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release_new_ctx = new;
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}
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break;
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}
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@ -617,6 +619,20 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
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__set_current_state(TASK_RUNNING);
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spin_unlock(&ctx->event_wqh.lock);
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if (release_new_ctx) {
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struct vm_area_struct *vma;
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struct mm_struct *mm = release_new_ctx->mm;
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/* the various vma->vm_userfaultfd_ctx still points to it */
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down_write(&mm->mmap_sem);
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for (vma = mm->mmap; vma; vma = vma->vm_next)
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if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx)
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vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
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up_write(&mm->mmap_sem);
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userfaultfd_ctx_put(release_new_ctx);
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}
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/*
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* ctx may go away after this if the userfault pseudo fd is
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* already released.
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