| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-56693: brd: defer automatic disk creation until module initialization succeeds |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2024-56693 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 5.15.174 with commit 41219c147df8bbd6591f59af5d695fb6c9a1cbff |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 6.1.120 with commit 259bf925583ec9e3781df778cadf00594095090d |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 6.6.64 with commit 410896624db639500f24f46478b4bfa05c76bf56 |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 6.11.11 with commit c0c2744cd2939ec5999c51dbaf2af16886548b7b |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 6.12.2 with commit 63dfd728b30f79495dacc886127695a379805152 |
| Issue introduced in 5.14 with commit 7f9b348cb5e94259acdcbafbcaed55d3bb515304 and fixed in 6.13 with commit 826cc42adf44930a633d11a5993676d85ddb0842 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-56693 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| drivers/block/brd.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| 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 |
