CVE-2025-38370

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: fix failure to rebuild free space tree using multiple transactions<br /> <br /> If we are rebuilding a free space tree, while modifying the free space<br /> tree we may need to allocate a new metadata block group.<br /> If we end up using multiple transactions for the rebuild, when we call<br /> btrfs_end_transaction() we enter btrfs_create_pending_block_groups()<br /> which calls add_block_group_free_space() to add items to the free space<br /> tree for the block group.<br /> <br /> Then later during the free space tree rebuild, at<br /> btrfs_rebuild_free_space_tree(), we may find such new block groups<br /> and call populate_free_space_tree() for them, which fails with -EEXIST<br /> because there are already items in the free space tree. Then we abort the<br /> transaction with -EEXIST at btrfs_rebuild_free_space_tree().<br /> Notice that we say "may find" the new block groups because a new block<br /> group may be inserted in the block groups rbtree, which is being iterated<br /> by the rebuild process, before or after the current node where the rebuild<br /> process is currently at.<br /> <br /> Syzbot recently reported such case which produces a trace like the<br /> following:<br /> <br /> ------------[ cut here ]------------<br /> BTRFS: Transaction aborted (error -17)<br /> WARNING: CPU: 1 PID: 7626 at fs/btrfs/free-space-tree.c:1341 btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1341<br /> Modules linked in:<br /> CPU: 1 UID: 0 PID: 7626 Comm: syz.2.25 Not tainted 6.15.0-rc7-syzkaller-00085-gd7fa1af5b33e-dirty #0 PREEMPT<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025<br /> pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)<br /> pc : btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1341<br /> lr : btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1341<br /> sp : ffff80009c4f7740<br /> x29: ffff80009c4f77b0 x28: ffff0000d4c3f400 x27: 0000000000000000<br /> x26: dfff800000000000 x25: ffff70001389eee8 x24: 0000000000000003<br /> x23: 1fffe000182b6e7b x22: 0000000000000000 x21: ffff0000c15b73d8<br /> x20: 00000000ffffffef x19: ffff0000c15b7378 x18: 1fffe0003386f276<br /> x17: ffff80008f31e000 x16: ffff80008adbe98c x15: 0000000000000001<br /> x14: 1fffe0001b281550 x13: 0000000000000000 x12: 0000000000000000<br /> x11: ffff60001b281551 x10: 0000000000000003 x9 : 1c8922000a902c00<br /> x8 : 1c8922000a902c00 x7 : ffff800080485878 x6 : 0000000000000000<br /> x5 : 0000000000000001 x4 : 0000000000000001 x3 : ffff80008047843c<br /> x2 : 0000000000000001 x1 : ffff80008b3ebc40 x0 : 0000000000000001<br /> Call trace:<br /> btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1341 (P)<br /> btrfs_start_pre_rw_mount+0xa78/0xe10 fs/btrfs/disk-io.c:3074<br /> btrfs_remount_rw fs/btrfs/super.c:1319 [inline]<br /> btrfs_reconfigure+0x828/0x2418 fs/btrfs/super.c:1543<br /> reconfigure_super+0x1d4/0x6f0 fs/super.c:1083<br /> do_remount fs/namespace.c:3365 [inline]<br /> path_mount+0xb34/0xde0 fs/namespace.c:4200<br /> do_mount fs/namespace.c:4221 [inline]<br /> __do_sys_mount fs/namespace.c:4432 [inline]<br /> __se_sys_mount fs/namespace.c:4409 [inline]<br /> __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4409<br /> __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]<br /> invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49<br /> el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132<br /> do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151<br /> el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767<br /> el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786<br /> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600<br /> irq event stamp: 330<br /> hardirqs last enabled at (329): [] raw_spin_rq_unlock_irq kernel/sched/sched.h:1525 [inline]<br /> hardirqs last enabled at (329): [] finish_lock_switch+0xb0/0x1c0 kernel/sched/core.c:5130<br /> hardirqs last disabled at (330): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:511<br /> softirqs last enabled at (10): [] local_bh_enable+0<br /> ---truncated---