[patch 101/114] pipe: fix off-by-one error when checking buffer limits

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From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxx
Fixes: b0b91d18e2e9 ("pipe: fix limit checking in pipe_set_size()")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Acked-by: Willy Tarreau <w@xxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Luis R . Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 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)
_



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