[PATCH 5.11 191/601] devtmpfs: fix placement of complete() call

Greg Kroah-Hartman
2021-05-12T17:13:14Z

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

[ Upstream commit 38f087de8947700d3b06d3d1594490e0f611c5d1 ]

Calling complete() from within the __init function is wrong -
theoretically, the init process could proceed all the way to freeing
the init mem before the devtmpfsd thread gets to execute the return
instruction in devtmpfs_setup().

In practice, it seems to be harmless as gcc inlines devtmpfs_setup()
into devtmpfsd(). So the calls of the __init functions init_chdir()
etc. actually happen from devtmpfs_setup(), but the __ref on that one
silences modpost (it's all right, because those calls happen before
the complete()). But it does make the __init annotation of the setup
function moot, which we'll fix in a subsequent patch.

Fixes: bcbacc4909f1 ("devtmpfs: refactor devtmpfsd()")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20210312103027.2701413-1-linux@rasmusvillemoes.dk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/base/devtmpfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index eac184e6d657..a71d14117943 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -416,7 +416,6 @@ static int __init devtmpfs_setup(void *p)
init_chroot(".");
out:
*(int *)p = err;
- complete(&setup_done);
return err;
}

@@ -429,6 +428,7 @@ static int __ref devtmpfsd(void *p)
{
int err = devtmpfs_setup(p);

+ complete(&setup_done);
if (err)
return err;
devtmpfs_work_loop();
--
2.30.2