linux-kernel - [PATCH 5.1 050/405] io_uring: use cpu_online() to check p->sq_thread_cpu instead of cpu

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Message-Id: <20190530030543.372257442@linuxfoundation.org>
Date:   Wed, 29 May 2019 20:00:48 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jeff Moyer <jmoyer@...hat.com>,
        Shenghui Wang <shhuiw@...mail.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.1 050/405] io_uring: use cpu_online() to check p->sq_thread_cpu instead of cpu_possible()

[ Upstream commit 7889f44dd9cee15aff1c3f7daf81ca4dfed48fc7 ]

This issue is found by running liburing/test/io_uring_setup test.

When test run, the testcase "attempt to bind to invalid cpu" would not
pass with messages like:
   io_uring_setup(1, 0xbfc2f7c8), \
flags: IORING_SETUP_SQPOLL|IORING_SETUP_SQ_AFF, \
resv: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000, \
sq_thread_cpu: 2
   expected -1, got 3
   FAIL

On my system, there is:
   CPU(s) possible : 0-3
   CPU(s) online   : 0-1
   CPU(s) offline  : 2-3
   CPU(s) present  : 0-1

The sq_thread_cpu 2 is offline on my system, so the bind should fail.
But cpu_possible() will pass the check. We shouldn't be able to bind
to an offline cpu. Use cpu_online() to do the check.

After the change, the testcase run as expected: EINVAL will be returned
for cpu offlined.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
Signed-off-by: Shenghui Wang <shhuiw@...mail.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 84efb8956734f..30a5687a17b65 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2334,7 +2334,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
 							nr_cpu_ids);
 
 			ret = -EINVAL;
-			if (!cpu_possible(cpu))
+			if (!cpu_online(cpu))
 				goto err;
 
 			ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
-- 
2.20.1