linux-kernel - [PATCH 5.4 027/107] kernel/relay.c: fix memleak on destroy relay channel

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Date:   Mon, 24 Aug 2020 10:29:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hulk Robot <hulkci@...wei.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Al Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        David Rientjes <rientjes@...gle.com>,
        Michel Lespinasse <walken@...gle.com>,
        Daniel Axtens <dja@...ens.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Akash Goel <akash.goel@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.4 027/107] kernel/relay.c: fix memleak on destroy relay channel

From: Wei Yongjun <weiyongjun1@...wei.com>

commit 71e843295c680898959b22dc877ae3839cc22470 upstream.

kmemleak report memory leak as follows:

  unreferenced object 0x607ee4e5f948 (size 8):
  comm "syz-executor.1", pid 2098, jiffies 4295031601 (age 288.468s)
  hex dump (first 8 bytes):
  00 00 00 00 00 00 00 00 ........
  backtrace:
     relay_open kernel/relay.c:583 [inline]
     relay_open+0xb6/0x970 kernel/relay.c:563
     do_blk_trace_setup+0x4a8/0xb20 kernel/trace/blktrace.c:557
     __blk_trace_setup+0xb6/0x150 kernel/trace/blktrace.c:597
     blk_trace_ioctl+0x146/0x280 kernel/trace/blktrace.c:738
     blkdev_ioctl+0xb2/0x6a0 block/ioctl.c:613
     block_ioctl+0xe5/0x120 fs/block_dev.c:1871
     vfs_ioctl fs/ioctl.c:48 [inline]
     __do_sys_ioctl fs/ioctl.c:753 [inline]
     __se_sys_ioctl fs/ioctl.c:739 [inline]
     __x64_sys_ioctl+0x170/0x1ce fs/ioctl.c:739
     do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
     entry_SYSCALL_64_after_hwframe+0x44/0xa9

'chan->buf' is malloced in relay_open() by alloc_percpu() but not free
while destroy the relay channel.  Fix it by adding free_percpu() before
return from relay_destroy_channel().

Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Daniel Axtens <dja@...ens.net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Akash Goel <akash.goel@...el.com>
Cc: <stable@...r.kernel.org>
Link: http://lkml.kernel.org/r/20200817122826.48518-1-weiyongjun1@huawei.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/relay.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -197,6 +197,7 @@ free_buf:
 static void relay_destroy_channel(struct kref *kref)
 {
 	struct rchan *chan = container_of(kref, struct rchan, kref);
+	free_percpu(chan->buf);
 	kfree(chan);
 }