Description
In the Linux kernel, the following vulnerability has been resolved: brd: defer automatic disk creation until module initialization succeeds My colleague Wupeng found the following problems during fault injection: BUG: unable to handle page fault for address: fffffbfff809d073 PGD 6e648067 P4D 123ec8067 PUD 123ec4067 PMD 100e38067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 5 UID: 0 PID: 755 Comm: modprobe Not tainted 6.12.0-rc3+ #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:__asan_load8+0x4c/0xa0 ... Call Trace: <TASK> blkdev_put_whole+0x41/0x70 bdev_release+0x1a3/0x250 blkdev_release+0x11/0x20 __fput+0x1d7/0x4a0 task_work_run+0xfc/0x180 syscall_exit_to_user_mode+0x1de/0x1f0 do_syscall_64+0x6b/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e loop_init() is calling loop_add() after __register_blkdev() succeeds and is ignoring disk_add() failure from loop_add(), for loop_add() failure is not fatal and successfully created disks are already visible to bdev_open(). brd_init() is currently calling brd_alloc() before __register_blkdev() succeeds and is releasing successfully created disks when brd_init() returns an error. This can cause UAF for the latter two case: case 1: T1: modprobe brd brd_init brd_alloc(0) // success add_disk disk_scan_partitions bdev_file_open_by_dev // alloc file fput // won't free until back to userspace brd_alloc(1) // failed since mem alloc error inject // error path for modprobe will release code segment // back to userspace __fput blkdev_release bdev_release blkdev_put_whole bdev->bd_disk->fops->release // fops is freed now, UAF! case 2: T1: T2: modprobe brd brd_init brd_alloc(0) // success open(/dev/ram0) brd_alloc(1) // fail // error path for modprobe close(/dev/ram0) ... /* UAF! */ bdev->bd_disk->fops->release Fix this problem by following what loop_init() does. Besides, reintroduce brd_devices_mutex to help serialize modifications to brd_list.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < 41219c147df8bbd6591f59af5d695fb6c9a1cbffaffected7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < 259bf925583ec9e3781df778cadf00594095090daffected7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < 410896624db639500f24f46478b4bfa05c76bf56affected7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < c0c2744cd2939ec5999c51dbaf2af16886548b7baffected7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < 63dfd728b30f79495dacc886127695a379805152affected7f9b348cb5e94259acdcbafbcaed55d3bb515304 to < 826cc42adf44930a633d11a5993676d85ddb0842affected
Linux Linux
Default version status: affected
5.14affected0 to < 5.14unaffected5.15.174 to ≤ 5.15.*unaffected6.1.120 to ≤ 6.1.*unaffected6.6.64 to ≤ 6.6.*unaffected6.11.11 to ≤ 6.11.*unaffected6.12.2 to ≤ 6.12.*unaffected6.13 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/41219c147df8bbd6591f59af5d695fb6c9a1cbff ↗
- https://git.kernel.org/stable/c/259bf925583ec9e3781df778cadf00594095090d ↗
- https://git.kernel.org/stable/c/410896624db639500f24f46478b4bfa05c76bf56 ↗
- https://git.kernel.org/stable/c/c0c2744cd2939ec5999c51dbaf2af16886548b7b ↗
- https://git.kernel.org/stable/c/63dfd728b30f79495dacc886127695a379805152 ↗
- https://git.kernel.org/stable/c/826cc42adf44930a633d11a5993676d85ddb0842 ↗
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html ↗