From: Eric Biggers ebiggers@google.com Subject: pipe: fix off-by-one error when checking buffer limits

With pipe-user-pages-hard set to 'N', users were actually only allowed up to 'N - 1' buffers; and likewise for pipe-user-pages-soft.

Fix this to allow up to 'N' buffers, as would be expected.

Link: http://lkml.kernel.org/r/20180111052902.14409-5-ebiggers3@gmail.com Fixes: b0b91d18e2e9 ("pipe: fix limit checking in pipe_set_size()") Signed-off-by: Eric Biggers ebiggers@google.com Acked-by: Willy Tarreau w@1wt.eu Acked-by: Kees Cook keescook@chromium.org Acked-by: Joe Lawrence joe.lawrence@redhat.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: "Luis R . Rodriguez" mcgrof@kernel.org Cc: Michael Kerrisk mtk.manpages@gmail.com Cc: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/pipe.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN fs/pipe.c~pipe-fix-off-by-one-error-when-checking-buffer-limits fs/pipe.c --- a/fs/pipe.c~pipe-fix-off-by-one-error-when-checking-buffer-limits +++ a/fs/pipe.c @@ -605,12 +605,12 @@ static unsigned long account_pipe_buffer

static bool too_many_pipe_buffers_soft(unsigned long user_bufs) { - return pipe_user_pages_soft && user_bufs >= pipe_user_pages_soft; + return pipe_user_pages_soft && user_bufs > pipe_user_pages_soft; }

static bool too_many_pipe_buffers_hard(unsigned long user_bufs) { - return pipe_user_pages_hard && user_bufs >= pipe_user_pages_hard; + return pipe_user_pages_hard && user_bufs > pipe_user_pages_hard; }

static bool is_unprivileged_user(void) _