[PATCH] fs: Check if automount actually mounts something

[PATCH] fs: Check if automount actually mounts something

[Sascha Hauer]

An automount command that returns successfully but doesn't mount
anything makes barebox hang as can be reproduced with:

automount -d /mnt/foo true
ls /mnt/foo

Check if the current dentry is a mountpoint after running the automount
command, otherwise return with an error from automount_mount().

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 fs/fs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/fs.c b/fs/fs.c
index 460fc2f7f1..bd6f144742 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -3191,6 +3191,10 @@ static int automount_mount(struct dentry *dentry)
 			printf("running automount command '%s' failed\n",
 					am->cmd);
 			ret = -ENODEV;
+		} else if (!(dentry->d_flags & DCACHE_MOUNTED)) {
+			printf("automount command '%s' didn't mount anything\n",
+					am->cmd);
+			ret = -ENODEV;
 		}
 
 		break;
-- 
2.30.2

Re: [PATCH] fs: Check if automount actually mounts something

[Uwe Kleine-König]

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On Thu, Jul 14, 2022 at 09:35:09PM +0200, Sascha Hauer wrote:
> An automount command that returns successfully but doesn't mount
> anything makes barebox hang as can be reproduced with:
> 
> automount -d /mnt/foo true
> ls /mnt/foo
> 
> Check if the current dentry is a mountpoint after running the automount
> command, otherwise return with an error from automount_mount().

While I think the intention of this patch is fine, I have little doubts
if that breaks some workflows, e.g. something like:

	automount -d /mnt/tralala 'for p in 0 1 2; do mkdir ${automount_path}/${p} && mount /dev/disk0.${p} ${automount_path}/${p} || break; done'

I admit it's a bit constructed, but maybe that's only because I'm not
creative enough?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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