On Mon, Feb 03, 2025 at 02:42:54AM -0800, Shubham Pushpkar wrote:
From: Zhihao Cheng chengzhihao1@huawei.com
commit aec8e6bf839101784f3ef037dcdb9432c3f32343 ("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:
Attach image_1 to loop0, attach image_2 to loop1, and scan btrfs devices by ioctl(BTRFS_IOC_SCAN_DEV):
/ btrfs_device_1 → loop0fs_device \ btrfs_device_2 → loop1
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)
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().
Fixes: CVE-2024-50217
Nit, as we assign CVEs _after_ a commit happens, there's no need to add this to a commit here as it is implied by the assignment database of cves-to-commits.
Also, any specific reason you didn't cc: everyone involved in this commit for your backport as well?
thanks,
greg k-h