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

Eric Biggers
2018-01-08T05:39:01Z

From: Eric Biggers <ebiggers@google.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.

Signed-off-by: Eric Biggers <ebiggers@google.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