Wind River Support Network

Description

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