CVE-2025-40100

*** Pendiente de traducción *** In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: do not assert we found block group item when creating free space tree<br /> <br /> Currently, when building a free space tree at populate_free_space_tree(),<br /> if we are not using the block group tree feature, we always expect to find<br /> block group items (either extent items or a block group item with key type<br /> BTRFS_BLOCK_GROUP_ITEM_KEY) when we search the extent tree with<br /> btrfs_search_slot_for_read(), so we assert that we found an item. However<br /> this expectation is wrong since we can have a new block group created in<br /> the current transaction which is still empty and for which we still have<br /> not added the block group&amp;#39;s item to the extent tree, in which case we do<br /> not have any items in the extent tree associated to the block group.<br /> <br /> The insertion of a new block group&amp;#39;s block group item in the extent tree<br /> happens at btrfs_create_pending_block_groups() when it calls the helper<br /> insert_block_group_item(). This typically is done when a transaction<br /> handle is released, committed or when running delayed refs (either as<br /> part of a transaction commit or when serving tickets for space reservation<br /> if we are low on free space).<br /> <br /> So remove the assertion at populate_free_space_tree() even when the block<br /> group tree feature is not enabled and update the comment to mention this<br /> case.<br /> <br /> Syzbot reported this with the following stack trace:<br /> <br /> BTRFS info (device loop3 state M): rebuilding free space tree<br /> assertion failed: ret == 0 :: 0, in fs/btrfs/free-space-tree.c:1115<br /> ------------[ cut here ]------------<br /> kernel BUG at fs/btrfs/free-space-tree.c:1115!<br /> Oops: invalid opcode: 0000 [#1] SMP KASAN PTI<br /> CPU: 1 UID: 0 PID: 6352 Comm: syz.3.25 Not tainted syzkaller #0 PREEMPT(full)<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025<br /> RIP: 0010:populate_free_space_tree+0x700/0x710 fs/btrfs/free-space-tree.c:1115<br /> Code: ff ff e8 d3 (...)<br /> RSP: 0018:ffffc9000430f780 EFLAGS: 00010246<br /> RAX: 0000000000000043 RBX: ffff88805b709630 RCX: fea61d0e2e79d000<br /> RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000<br /> RBP: ffffc9000430f8b0 R08: ffffc9000430f4a7 R09: 1ffff92000861e94<br /> R10: dffffc0000000000 R11: fffff52000861e95 R12: 0000000000000001<br /> R13: 1ffff92000861f00 R14: dffffc0000000000 R15: 0000000000000000<br /> FS: 00007f424d9fe6c0(0000) GS:ffff888125afc000(0000) knlGS:0000000000000000<br /> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> CR2: 00007fd78ad212c0 CR3: 0000000076d68000 CR4: 00000000003526f0<br /> Call Trace:<br /> <br /> btrfs_rebuild_free_space_tree+0x1ba/0x6d0 fs/btrfs/free-space-tree.c:1364<br /> btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3062<br /> btrfs_remount_rw fs/btrfs/super.c:1334 [inline]<br /> btrfs_reconfigure+0xaed/0x2160 fs/btrfs/super.c:1559<br /> reconfigure_super+0x227/0x890 fs/super.c:1076<br /> do_remount fs/namespace.c:3279 [inline]<br /> path_mount+0xd1a/0xfe0 fs/namespace.c:4027<br /> do_mount fs/namespace.c:4048 [inline]<br /> __do_sys_mount fs/namespace.c:4236 [inline]<br /> __se_sys_mount+0x313/0x410 fs/namespace.c:4213<br /> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]<br /> do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94<br /> entry_SYSCALL_64_after_hwframe+0x77/0x7f<br /> RIP: 0033:0x7f424e39066a<br /> Code: d8 64 89 02 (...)<br /> RSP: 002b:00007f424d9fde68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5<br /> RAX: ffffffffffffffda RBX: 00007f424d9fdef0 RCX: 00007f424e39066a<br /> RDX: 0000200000000180 RSI: 0000200000000380 RDI: 0000000000000000<br /> RBP: 0000200000000180 R08: 00007f424d9fdef0 R09: 0000000000000020<br /> R10: 0000000000000020 R11: 0000000000000246 R12: 0000200000000380<br /> R13: 00007f424d9fdeb0 R14: 0000000000000000 R15: 00002000000002c0<br /> <br /> Modules linked in:<br /> ---[ end trace 0000000000000000 ]---