linux-kernel - [PATCH AUTOSEL 6.9 06/15] io_uring/sqpoll: work around a potential audit memory leak

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Date: Sun, 26 May 2024 05:41:38 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>,
	Sasha Levin <sashal@...nel.org>,
	io-uring@...r.kernel.org
Subject: [PATCH AUTOSEL 6.9 06/15] io_uring/sqpoll: work around a potential audit memory leak

From: Jens Axboe <axboe@...nel.dk>

[ Upstream commit c4ce0ab27646f4206a9eb502d6fe45cb080e1cae ]

kmemleak complains that there's a memory leak related to connect
handling:

unreferenced object 0xffff0001093bdf00 (size 128):
comm "iou-sqp-455", pid 457, jiffies 4294894164
hex dump (first 32 bytes):
02 00 fa ea 7f 00 00 01 00 00 00 00 00 00 00 00  ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
backtrace (crc 2e481b1a):
[<00000000c0a26af4>] kmemleak_alloc+0x30/0x38
[<000000009c30bb45>] kmalloc_trace+0x228/0x358
[<000000009da9d39f>] __audit_sockaddr+0xd0/0x138
[<0000000089a93e34>] move_addr_to_kernel+0x1a0/0x1f8
[<000000000b4e80e6>] io_connect_prep+0x1ec/0x2d4
[<00000000abfbcd99>] io_submit_sqes+0x588/0x1e48
[<00000000e7c25e07>] io_sq_thread+0x8a4/0x10e4
[<00000000d999b491>] ret_from_fork+0x10/0x20

which can can happen if:

1) The command type does something on the prep side that triggers an
   audit call.
2) The thread hasn't done any operations before this that triggered
   an audit call inside ->issue(), where we have audit_uring_entry()
   and audit_uring_exit().

Work around this by issuing a blanket NOP operation before the SQPOLL
does anything.

Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 io_uring/sqpoll.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 3983708cef5b4..554c7212aa463 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -291,6 +291,14 @@ static int io_sq_thread(void *data)
 		sqd->sq_cpu = raw_smp_processor_id();
 	}
 
+	/*
+	 * Force audit context to get setup, in case we do prep side async
+	 * operations that would trigger an audit call before any issue side
+	 * audit has been done.
+	 */
+	audit_uring_entry(IORING_OP_NOP);
+	audit_uring_exit(true, 0);
+
 	mutex_lock(&sqd->lock);
 	while (1) {
 		bool cap_entries, sqt_spin = false;
-- 
2.43.0