linux-kernel - [PATCH v2 4/7] pipe: fix off-by-one error when checking buffer limits

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Message-Id: <20180111052902.14409-5-ebiggers3@gmail.com>
Date:   Wed, 10 Jan 2018 21:28:59 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Willy Tarreau <w@....eu>,
        Mikulas Patocka <mpatocka@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        stable@...r.kernel.org
Subject: [PATCH v2 4/7] pipe: fix off-by-one error when checking buffer limits

From: Eric Biggers <ebiggers@...gle.com>

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.

Fixes: b0b91d18e2e9 ("pipe: fix limit checking in pipe_set_size()")
Cc: stable@...r.kernel.org
Acked-by: Willy Tarreau <w@....eu>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/pipe.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 847ecc388820..9f20e7128578 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -605,12 +605,12 @@ static unsigned long account_pipe_buffers(struct user_struct *user,
 
 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)
-- 
2.15.1