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Wed, 14 Jan 2026 18:59:57 -0800 (PST) X-Relaying-Domain: purestorage.com Received: from dev-sconnor.dev.purestorage.com (unknown [IPv6:2620:125:9007:640:ffff::4936]) by c7-smtp-2023.dev.purestorage.com (Postfix) with ESMTP id 2BCC034040C; Wed, 14 Jan 2026 19:59:57 -0700 (MST) From: Seamus Connor To: Ming Lei , Jens Axboe , linux-block@vger.kernel.org Cc: Seamus Connor , Caleb Sander Mateos Subject: [PATCH v4] ublk: fix ublksrv pid handling for pid namespaces Date: Wed, 14 Jan 2026 18:59:52 -0800 Message-ID: <20260115025952.2321238-1-sconnor@purestorage.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When ublksrv runs inside a pid namespace, START/END_RECOVERY compared the stored init-ns tgid against the userspace pid (getpid vnr), so the check failed and control ops could not proceed. Compare against the caller’s init-ns tgid and store that value, then translate it back to the caller’s pid namespace when reporting GET_DEV_INFO so ublk list shows a sensible pid. Testing: start/recover in a pid namespace; `ublk list` shows reasonable pid values in init, child, and sibling namespaces. Fixes: d37a224fc119 ("ublk: validate ublk server pid") Signed-off-by: Seamus Connor Reviewed-by: Caleb Sander Mateos Reviewed-by: Ming Lei --- Changes since v1: - Updated start_dev and end_recovery to respect the user-supplied pid Changes since v2: - Moved pid translation into a helper function Changes since v3: - Minor rework to the helper function drivers/block/ublk_drv.c | 39 ++++++++++++++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 5 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 67d4a867aec4..898c17755135 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -2852,6 +2852,15 @@ static struct ublk_device *ublk_get_device_from_id(int idx) return ub; } +static bool ublk_validate_user_pid(struct ublk_device *ub, pid_t ublksrv_pid) +{ + rcu_read_lock(); + ublksrv_pid = pid_nr(find_vpid(ublksrv_pid)); + rcu_read_unlock(); + + return ub->ublksrv_tgid == ublksrv_pid; +} + static int ublk_ctrl_start_dev(struct ublk_device *ub, const struct ublksrv_ctrl_cmd *header) { @@ -2920,7 +2929,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, if (wait_for_completion_interruptible(&ub->completion) != 0) return -EINTR; - if (ub->ublksrv_tgid != ublksrv_pid) + if (!ublk_validate_user_pid(ub, ublksrv_pid)) return -EINVAL; mutex_lock(&ub->mutex); @@ -2939,7 +2948,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, disk->fops = &ub_fops; disk->private_data = ub; - ub->dev_info.ublksrv_pid = ublksrv_pid; + ub->dev_info.ublksrv_pid = ub->ublksrv_tgid; ub->ub_disk = disk; ublk_apply_params(ub); @@ -3274,12 +3283,32 @@ static int ublk_ctrl_stop_dev(struct ublk_device *ub) static int ublk_ctrl_get_dev_info(struct ublk_device *ub, const struct ublksrv_ctrl_cmd *header) { + struct task_struct *p; + struct pid *pid; + struct ublksrv_ctrl_dev_info dev_info; + pid_t init_ublksrv_tgid = ub->dev_info.ublksrv_pid; void __user *argp = (void __user *)(unsigned long)header->addr; if (header->len < sizeof(struct ublksrv_ctrl_dev_info) || !header->addr) return -EINVAL; - if (copy_to_user(argp, &ub->dev_info, sizeof(ub->dev_info))) + memcpy(&dev_info, &ub->dev_info, sizeof(dev_info)); + dev_info.ublksrv_pid = -1; + + if (init_ublksrv_tgid > 0) { + rcu_read_lock(); + pid = find_pid_ns(init_ublksrv_tgid, &init_pid_ns); + p = pid_task(pid, PIDTYPE_TGID); + if (p) { + int vnr = task_tgid_vnr(p); + + if (vnr) + dev_info.ublksrv_pid = vnr; + } + rcu_read_unlock(); + } + + if (copy_to_user(argp, &dev_info, sizeof(dev_info))) return -EFAULT; return 0; @@ -3424,7 +3453,7 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub, pr_devel("%s: All FETCH_REQs received, dev id %d\n", __func__, header->dev_id); - if (ub->ublksrv_tgid != ublksrv_pid) + if (!ublk_validate_user_pid(ub, ublksrv_pid)) return -EINVAL; mutex_lock(&ub->mutex); @@ -3435,7 +3464,7 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub, ret = -EBUSY; goto out_unlock; } - ub->dev_info.ublksrv_pid = ublksrv_pid; + ub->dev_info.ublksrv_pid = ub->ublksrv_tgid; ub->dev_info.state = UBLK_S_DEV_LIVE; pr_devel("%s: new ublksrv_pid %d, dev id %d\n", __func__, ublksrv_pid, header->dev_id); -- 2.43.0