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fuse: Fix use-after-free in fuse_dev_do_write() 

After we found req in request_find() and released the lock,
everything may happen with the req in parallel:

cpu0                              cpu1
fuse_dev_do_write()               fuse_dev_do_write()
  req = request_find(fpq, ...)    ...
  spin_unlock(&fpq->lock)         ...
  ...                             req = request_find(fpq, oh.unique)
  ...                             spin_unlock(&fpq->lock)
  queue_interrupt(&fc->iq, req);   ...
  ...                              ...
  ...                              ...
  request_end(fc, req);
    fuse_put_request(fc, req);
  ...                              queue_interrupt(&fc->iq, req);


Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 46c34a348b ("fuse: no fc->lock for pqueue parts")
Cc: <stable@vger.kernel.org> # v4.2
This commit is contained in:
Kirill Tkhai 2018-09-25 12:52:42 +03:00 committed by Miklos Szeredi
parent bc78abbd55
commit d2d2d4fb1f
1 changed files with 5 additions and 1 deletions
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6
fs/fuse/dev.c
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@ -1877,16 +1877,20 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
/* Is it an interrupt reply? */
if (req->intr_unique == oh.unique) {
__fuse_get_request(req);
spin_unlock(&fpq->lock);
err = -EINVAL;
if (nbytes != sizeof(struct fuse_out_header))
if (nbytes != sizeof(struct fuse_out_header)) {
fuse_put_request(fc, req);
goto err_finish;
}
if (oh.error == -ENOSYS)
fc->no_interrupt = 1;
else if (oh.error == -EAGAIN)
queue_interrupt(&fc->iq, req);
fuse_put_request(fc, req);
fuse_copy_finish(cs);
return nbytes;