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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Eric Biggers <ebiggers@google.com>,
        Willy Tarreau <w@1wt.eu>, Kees Cook <keescook@chromium.org>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Luis R . Rodriguez" <mcgrof@kernel.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.15 160/202] pipe: fix off-by-one error when checking buffer limits
Date:   Thu, 15 Feb 2018 16:17:40 +0100
Message-Id: <20180215151721.258637616@linuxfoundation.org>
In-Reply-To: <20180215151712.768794354@linuxfoundation.org>
References: <20180215151712.768794354@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

commit 9903a91c763ecdae333a04a9d89d79d2b8966503 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -610,12 +610,12 @@ 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)