fuse: fix use-after-free in fuse_direct_IO()
commit ebacb812 upstream. In async IO blocking case the additional reference to the io is taken for it to survive fuse_aio_complete(). In non blocking case this additional reference is not needed, however we still reference io to figure out whether to wait for completion or not. This is wrong and will lead to use-after-free. Fix it by storing blocking information in separate variable. This was spotted by KASAN when running generic/208 fstest. Signed-off-by: NLukas Czerner <lczerner@redhat.com> Reported-by: NZorro Lang <zlang@redhat.com> Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com> Fixes: 744742d6 ("fuse: Add reference counting for fuse_io_priv") Cc: <stable@vger.kernel.org> # v4.6 Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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