tree ca221e796b274a6c909db003fcda215156aa4cc7
parent 4d22c75d4c7b5c5f4bd31054f09103ee490878fd
author Al Viro <viro@zeniv.linux.org.uk> 1484440388 -0500
committer Al Viro <viro@zeniv.linux.org.uk> 1484441441 -0500

fix a fencepost error in pipe_advance()

The logics in pipe_advance() used to release all buffers past the new
position failed in cases when the number of buffers to release was equal
to pipe->buffers.  If that happened, none of them had been released,
leaving pipe full.  Worse, it was trivial to trigger and we end up with
pipe full of uninitialized pages.  IOW, it's an infoleak.

Cc: stable@vger.kernel.org # v4.9
Reported-by: "Alan J. Wylie" <alan@wylie.me.uk>
Tested-by: "Alan J. Wylie" <alan@wylie.me.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>