CVE-2024-50217 Information

Nov 10, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()

Mounting btrfs from two images (which have the same one fsid and two different dev_uuids) in certain executing order may trigger an UAF for variable ‘device->bdev_file’ in __btrfs_free_extra_devids(). And following are the details:

  1. Attach image_1 to loop0 attach image_2 to loop1 and scan btrfs devices by ioctl(BTRFS_IOC_SCAN_DEV):

          /  btrfs_device_1 ? loop0

    fs_device \ btrfs_device_2 ? loop1

  2. mount /dev/loop0 /mnt btrfs_open_devices btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0) btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree fail: btrfs_close_devices // -ENOMEM btrfs_close_bdev(btrfs_device_1) fput(btrfs_device_1->bdev_file) // btrfs_device_1->bdev_file is freed btrfs_close_bdev(btrfs_device_2) fput(btrfs_device_2->bdev_file)

  3. mount /dev/loop1 /mnt btrfs_open_devices btrfs_get_bdev_and_sb(&bdev_file) // EIO btrfs_device_1->bdev_file is not assigned // which points to a freed memory area btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1) btrfs_fill_super open_ctree btrfs_free_extra_devids if (btrfs_device_1->bdev_file) fput(btrfs_device_1->bdev_file) // UAF !

Fix it by setting ‘device->bdev_file’ as ‘NULL’ after closing the btrfs_device in btrfs_close_one_device().

Reference

https://git.kernel.org/stable/c/47a83f8df39545f3f552bb6a1b6d9c30e37621dd https://git.kernel.org/stable/c/aec8e6bf839101784f3ef037dcdb9432c3f32343

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