queue-6.6/ublk-prevent-invalid-access-with-debug.patch

From 4a217388c856e78ca76733c603047a2bbb3e1f2b Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Wed, 26 Nov 2025 12:48:35 +0000
Subject: ublk: prevent invalid access with DEBUG

From: Kevin Brodsky <kevin.brodsky@arm.com>

[ Upstream commit c6a45ee7607de3a350008630f4369b1b5ac80884 ]

ublk_ch_uring_cmd_local() may jump to the out label before
initialising the io pointer. This will cause trouble if DEBUG is
defined, because the pr_devel() call dereferences io. Clang reports:

drivers/block/ublk_drv.c:2403:6: error: variable 'io' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
 2403 |         if (tag >= ub->dev_info.queue_depth)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/block/ublk_drv.c:2492:32: note: uninitialized use occurs here
 2492 |                         __func__, cmd_op, tag, ret, io->flags);
      |

Fix this by initialising io to NULL and checking it before
dereferencing it.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Fixes: 71f28f3136af ("ublk_drv: add io_uring based userspace block driver")
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/ublk_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 88d566f0ffa64..563b2a94d4c3c 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1709,7 +1709,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 {
 	struct ublk_device *ub = cmd->file->private_data;
 	struct ublk_queue *ubq;
-	struct ublk_io *io;
+	struct ublk_io *io = NULL;
 	u32 cmd_op = cmd->cmd_op;
 	unsigned tag = ub_cmd->tag;
 	int ret = -EINVAL;
@@ -1822,7 +1822,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 
  out:
 	pr_devel("%s: complete: cmd op %d, tag %d ret %x io_flags %x\n",
-			__func__, cmd_op, tag, ret, io->flags);
+			__func__, cmd_op, tag, ret, io ? io->flags : 0);
 	return ret;
 }
 
-- 
2.51.0