Re: [dm-devel] [PATCH] dm raid: add missed unlock in raid_ctr

[Heinz Mauelshagen <heinzm@redhat.com>]

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On Fri, Sep 3, 2021 at 10:02 AM Dinghao Liu <dinghao.liu@zju.edu.cn> wrote:

> mddev_unlock() is called on all paths after we call mddev_lock_nointr(),
> except for three error handling paths, which may cause a deadlock. This
> bug is suggested by a static analysis tool, please advise.
>

Hi,

correct, those unlock calls are missing.

As we are bailing out after md_run() with lock held,
we can clean the lot of error paths underneath up by jumping to before
md_stop() and add the mddev_unlock upfront it like:

>From 5c72f1d07195127f5fd49bccbe0705854463c199 Mon Sep 17 00:00:00 2001
Message-Id: <
5c72f1d07195127f5fd49bccbe0705854463c199.1630675612.git.heinzm@redhat.com>
From: Heinz Mauelshagen <heinzm@redhat.com>
Date: Fri, 3 Sep 2021 15:26:50 +0200
Subject: [PATCH] dm raid: fix mddev unlocking in raid_ctr() error paths

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
---
 drivers/md/dm-raid.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index d9ef52159a22..741bab00e922 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3249,14 +3249,12 @@ static int raid_ctr(struct dm_target *ti, unsigned
int argc, char **argv)
        rs->md.in_sync = 0; /* Assume already marked dirty */
        if (r) {
                ti->error = "Failed to run raid array";
-               mddev_unlock(&rs->md);
-               goto bad;
+               goto bad_unlock;
        }

        r = md_start(&rs->md);
        if (r) {
                ti->error = "Failed to start raid array";
-               mddev_unlock(&rs->md);
                goto bad_md_start;
        }

@@ -3265,7 +3263,6 @@ static int raid_ctr(struct dm_target *ti, unsigned
int argc, char **argv)
                r = r5c_journal_mode_set(&rs->md, rs->journal_dev.mode);
                if (r) {
                        ti->error = "Failed to set raid4/5/6 journal mode";
-                       mddev_unlock(&rs->md);
                        goto bad_journal_mode_set;
                }
        }
@@ -3304,10 +3301,12 @@ static int raid_ctr(struct dm_target *ti, unsigned
int argc, char **argv)
        mddev_unlock(&rs->md);
        return 0;

+bad_unlock:
 bad_md_start:
 bad_journal_mode_set:
 bad_stripe_cache:
 bad_check_reshape:
+       mddev_unlock(&rs->md);
        md_stop(&rs->md);
 bad:
        raid_set_free(rs);
-- 
2.31.1


-- lvmguy


>
> Fixes: 9dbd1aa3a81c ("dm raid: add reshaping support to the target")
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> ---
>  drivers/md/dm-raid.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index d9ef52159a22..79f36a806082 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -3276,15 +3276,19 @@ static int raid_ctr(struct dm_target *ti, unsigned
> int argc, char **argv)
>         /* Try to adjust the raid4/5/6 stripe cache size to the stripe
> size */
>         if (rs_is_raid456(rs)) {
>                 r = rs_set_raid456_stripe_cache(rs);
> -               if (r)
> +               if (r) {
> +                       mddev_unlock(&rs->md);
>                         goto bad_stripe_cache;
> +               }
>         }
>
>         /* Now do an early reshape check */
>         if (test_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
>                 r = rs_check_reshape(rs);
> -               if (r)
> +               if (r) {
> +                       mddev_unlock(&rs->md);
>                         goto bad_check_reshape;
> +               }
>
>                 /* Restore new, ctr requested layout to perform check */
>                 rs_config_restore(rs, &rs_layout);
> @@ -3293,6 +3297,7 @@ static int raid_ctr(struct dm_target *ti, unsigned
> int argc, char **argv)
>                         r = rs->md.pers->check_reshape(&rs->md);
>                         if (r) {
>                                 ti->error = "Reshape check failed";
> +                               mddev_unlock(&rs->md);
>                                 goto bad_check_reshape;
>                         }
>                 }
> --
> 2.17.1
>
>

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