| From bippy-1.2.0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@kernel.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-26944: btrfs: zoned: fix use-after-free in do_zone_finish() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| btrfs: zoned: fix use-after-free in do_zone_finish() |
| |
| Shinichiro reported the following use-after-free triggered by the device |
| replace operation in fstests btrfs/070. |
| |
| BTRFS info (device nullb1): scrub: finished on devid 1 with status: 0 |
| ================================================================== |
| BUG: KASAN: slab-use-after-free in do_zone_finish+0x91a/0xb90 [btrfs] |
| Read of size 8 at addr ffff8881543c8060 by task btrfs-cleaner/3494007 |
| |
| CPU: 0 PID: 3494007 Comm: btrfs-cleaner Tainted: G W 6.8.0-rc5-kts #1 |
| Hardware name: Supermicro Super Server/X11SPi-TF, BIOS 3.3 02/21/2020 |
| Call Trace: |
| <TASK> |
| dump_stack_lvl+0x5b/0x90 |
| print_report+0xcf/0x670 |
| ? __virt_addr_valid+0x200/0x3e0 |
| kasan_report+0xd8/0x110 |
| ? do_zone_finish+0x91a/0xb90 [btrfs] |
| ? do_zone_finish+0x91a/0xb90 [btrfs] |
| do_zone_finish+0x91a/0xb90 [btrfs] |
| btrfs_delete_unused_bgs+0x5e1/0x1750 [btrfs] |
| ? __pfx_btrfs_delete_unused_bgs+0x10/0x10 [btrfs] |
| ? btrfs_put_root+0x2d/0x220 [btrfs] |
| ? btrfs_clean_one_deleted_snapshot+0x299/0x430 [btrfs] |
| cleaner_kthread+0x21e/0x380 [btrfs] |
| ? __pfx_cleaner_kthread+0x10/0x10 [btrfs] |
| kthread+0x2e3/0x3c0 |
| ? __pfx_kthread+0x10/0x10 |
| ret_from_fork+0x31/0x70 |
| ? __pfx_kthread+0x10/0x10 |
| ret_from_fork_asm+0x1b/0x30 |
| </TASK> |
| |
| Allocated by task 3493983: |
| kasan_save_stack+0x33/0x60 |
| kasan_save_track+0x14/0x30 |
| __kasan_kmalloc+0xaa/0xb0 |
| btrfs_alloc_device+0xb3/0x4e0 [btrfs] |
| device_list_add.constprop.0+0x993/0x1630 [btrfs] |
| btrfs_scan_one_device+0x219/0x3d0 [btrfs] |
| btrfs_control_ioctl+0x26e/0x310 [btrfs] |
| __x64_sys_ioctl+0x134/0x1b0 |
| do_syscall_64+0x99/0x190 |
| entry_SYSCALL_64_after_hwframe+0x6e/0x76 |
| |
| Freed by task 3494056: |
| kasan_save_stack+0x33/0x60 |
| kasan_save_track+0x14/0x30 |
| kasan_save_free_info+0x3f/0x60 |
| poison_slab_object+0x102/0x170 |
| __kasan_slab_free+0x32/0x70 |
| kfree+0x11b/0x320 |
| btrfs_rm_dev_replace_free_srcdev+0xca/0x280 [btrfs] |
| btrfs_dev_replace_finishing+0xd7e/0x14f0 [btrfs] |
| btrfs_dev_replace_by_ioctl+0x1286/0x25a0 [btrfs] |
| btrfs_ioctl+0xb27/0x57d0 [btrfs] |
| __x64_sys_ioctl+0x134/0x1b0 |
| do_syscall_64+0x99/0x190 |
| entry_SYSCALL_64_after_hwframe+0x6e/0x76 |
| |
| The buggy address belongs to the object at ffff8881543c8000 |
| which belongs to the cache kmalloc-1k of size 1024 |
| The buggy address is located 96 bytes inside of |
| freed 1024-byte region [ffff8881543c8000, ffff8881543c8400) |
| |
| The buggy address belongs to the physical page: |
| page:00000000fe2c1285 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1543c8 |
| head:00000000fe2c1285 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 |
| flags: 0x17ffffc0000840(slab|head|node=0|zone=2|lastcpupid=0x1fffff) |
| page_type: 0xffffffff() |
| raw: 0017ffffc0000840 ffff888100042dc0 ffffea0019e8f200 dead000000000002 |
| raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 |
| page dumped because: kasan: bad access detected |
| |
| Memory state around the buggy address: |
| ffff8881543c7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |
| ffff8881543c7f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |
| >ffff8881543c8000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ^ |
| ffff8881543c8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ffff8881543c8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| |
| This UAF happens because we're accessing stale zone information of a |
| already removed btrfs_device in do_zone_finish(). |
| |
| The sequence of events is as follows: |
| |
| btrfs_dev_replace_start |
| btrfs_scrub_dev |
| btrfs_dev_replace_finishing |
| btrfs_dev_replace_update_device_in_mapping_tree <-- devices replaced |
| btrfs_rm_dev_replace_free_srcdev |
| btrfs_free_device <-- device freed |
| |
| cleaner_kthread |
| btrfs_delete_unused_bgs |
| btrfs_zone_finish |
| do_zone_finish <-- refers the freed device |
| |
| The reason for this is that we're using a cached pointer to the chunk_map |
| from the block group, but on device replace this cached pointer can |
| contain stale device entries. |
| |
| The staleness comes from the fact, that btrfs_block_group::physical_map is |
| not a pointer to a btrfs_chunk_map but a memory copy of it. |
| |
| Also take the fs_info::dev_replace::rwsem to prevent |
| btrfs_dev_replace_update_device_in_mapping_tree() from changing the device |
| underneath us again. |
| |
| Note: btrfs_dev_replace_update_device_in_mapping_tree() is holding |
| fs_info::mapping_tree_lock, but as this is a spinning read/write lock we |
| cannot take it as the call to blkdev_zone_mgmt() requires a memory |
| allocation which may not sleep. |
| But btrfs_dev_replace_update_device_in_mapping_tree() is always called with |
| the fs_info::dev_replace::rwsem held in write mode. |
| |
| Many thanks to Shinichiro for analyzing the bug. |
| |
| The Linux kernel CVE team has assigned CVE-2024-26944 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.18 with commit 4dcbb8ab31c1292aea6a3f240e19523f633320c2 and fixed in 6.8.3 with commit 34ca809e055eca5cfe63d9c7efbf80b7c21b4e57 |
| Issue introduced in 5.18 with commit 4dcbb8ab31c1292aea6a3f240e19523f633320c2 and fixed in 6.9 with commit 1ec17ef59168a1a6f1105f5dc517f783839a5302 |
| |
| 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-2024-26944 |
| 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: |
| fs/btrfs/zoned.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/34ca809e055eca5cfe63d9c7efbf80b7c21b4e57 |
| https://git.kernel.org/stable/c/1ec17ef59168a1a6f1105f5dc517f783839a5302 |
