CVE-2024-26944: 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 ---truncated---