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Wed, 14 Oct 2026 04:53:35 -0700 (PDT) Received: from jwang-ThinkPad-T14-Gen-6.fkb.profitbricks.net ([212.227.34.98]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de3f7f8b8sm10170728f8f.35.2026.10.14.04.53.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2026 04:53:35 -0700 (PDT) From: Jack Wang To: Song Liu , Yu Kuai Cc: Li Nan , Xiao Ni , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Jack Wang Subject: [PATCH v2] md: clear MD_CLOSING when array_state_store() bails on interrupted lock Date: Wed, 14 Oct 2026 13:53:34 +0200 Message-ID: <20261014115334.619923-1-jinpu.wang@ionos.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jack Wang Writing "clear", "readonly", "inactive" or "read_auto" to array_state calls mddev_set_closing_and_sync_blockdev(), which sets MD_CLOSING to keep the array from being reopened while it is torn down. The flag is only cleared again at the tail of array_state_store() (for readonly / read_auto / inactive, or the failed-clear case). Between setting the flag and reaching that tail there is an early return: err = mddev_lock(mddev); if (err) return err; mddev_lock() is mutex_lock_interruptible() on reconfig_mutex. If the writing task catches a signal while blocked there, it returns -EINTR and MD_CLOSING is left set on a still-running array. do_md_stop() / md_set_readonly() never ran, so the array keeps working internally, but every subsequent md_open() now returns -ENODEV for all callers - the device shows up in /proc/mdstat and sysfs is fully populated, yet cannot be opened, and cannot be recovered without a reboot (all clear paths either need the device open or re-enter test_and_set_bit(MD_CLOSING) and bail with -EBUSY before the clear). The window is easy to hit on a busy host: reconfig_mutex is held for long stretches by a running resync/recovery, widening the interruptible wait, and a userspace helper writing to array_state and then being killed or timed out is enough to leak the flag. Route the interrupted-lock exit through a common label so the flag is released. Guard the clear with a set_closing flag that records whether this write actually set MD_CLOSING: when mddev->pers is already NULL (for example a concurrent STOP_ARRAY is mid-teardown) this write skips the mddev_set_closing_and_sync_blockdev() call above, so it must not clear a MD_CLOSING that the other thread owns - doing so could let the array be reopened while it is being destroyed. This also tightens the pre-existing tail clear, which had the same unconditional behaviour. mddev_unlock() is correctly skipped on the goto path since the lock was never acquired. Fixes: 99b902ac1725 ("md: sync blockdev before stopping raid or setting readonly") Assisted-by: Claude:claude-opus-4-8 [Claude Code] Signed-off-by: Jack Wang --- v2: resend, rebased on md-7.4-20261013 (md/md-7.4), no code changes. drivers/md/md.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 03e35386a802..f6dfd5d76199 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4671,6 +4671,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) { int err = 0; enum array_state st = match_word(buf, array_states); + bool set_closing = false; /* No lock dependent actions */ switch (st) { @@ -4691,6 +4692,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) err = mddev_set_closing_and_sync_blockdev(mddev, 0); if (err) return err; + set_closing = true; break; default: break; @@ -4719,7 +4721,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) } err = mddev_lock(mddev); if (err) - return err; + goto out_clear_closing; switch (st) { case inactive: @@ -4792,8 +4794,17 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) } mddev_unlock(mddev); - if (st == readonly || st == read_auto || st == inactive || - (err && st == clear)) +out_clear_closing: + /* + * Only clear MD_CLOSING if this write actually set it. Otherwise a + * concurrent teardown (e.g. STOP_ARRAY) may own the flag - this write + * would have skipped setting it above when mddev->pers was already + * NULL - and clearing it here would let the array be reopened while it + * is being destroyed. + */ + if (set_closing && + (st == readonly || st == read_auto || st == inactive || + (err && st == clear))) clear_bit(MD_CLOSING, &mddev->flags); return err ?: len; -- 2.43.0