Re: [PATCH] ubi: block: fix null-pointer-dereference in ubiblock_create()

From: Li Nan
Date: Mon May 06 2024 - 09:38:00 EST




在 2024/4/28 15:51, Zhihao Cheng 写道:
在 2024/4/28 15:19, linan666@xxxxxxxxxxxxxxx 写道:
From: Li Nan <linan122@xxxxxxxxxx>

Similar to commit adbf4c4954e3 ("ubi: block: fix memleak in
ubiblock_create()"), 'dev->gd' is not assigned but dereferenced if
blk_mq_alloc_tag_set() fails, and leading to a null-pointer-dereference.

Using 'gd' directly here is not a good idea, too. 'gd->part0.bd_device'
is not initialized at this point. The error log will be:
   block (null): block: dynamic minor allocation failed

Fix it by using pr_err() and print ubi id.

Fixes: 77567b25ab9f ("ubi: use blk_mq_alloc_disk and blk_cleanup_disk")
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
---
  drivers/mtd/ubi/block.c | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
index f82e3423acb9..bf7308e8ec2f 100644
--- a/drivers/mtd/ubi/block.c
+++ b/drivers/mtd/ubi/block.c
@@ -390,7 +390,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
      ret = blk_mq_alloc_tag_set(&dev->tag_set);
      if (ret) {
-        dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
+        pr_err("ubiblock%d_%d: blk_mq_alloc_tag_set failed\n",
+            dev->ubi_num, dev->vol_id);
          goto out_free_dev;
      }
@@ -407,8 +408,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
      gd->minors = 1;
      gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, GFP_KERNEL);

There is no need to modify this place. The device of 'gd' is initialized in blk_mq_alloc_disk. Refer to nbd_dev_add.


The print of this dev_err() is:
block (null): block: dynamic minor allocation failed
~~~~~~
There is no information about which device failed. dev_err()
use 'kobject_name(&dev->kobj)' here, which is init in device_add_disk()
later. So use pr_err() here can print more detail.

I will split the patch into two in v2 to make it clearer.

      if (gd->first_minor < 0) {
-        dev_err(disk_to_dev(gd),
-            "block: dynamic minor allocation failed");
+        pr_err("ubiblock%d_%d: block: dynamic minor allocation failed\n",
+            dev->ubi_num, dev->vol_id);
          ret = -ENODEV;
          goto out_cleanup_disk;
      }


--
Thanks,
Nan