CVE-2024-42111

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: always do the basic checks for btrfs_qgroup_inherit structure<br /> <br /> [BUG]<br /> Syzbot reports the following regression detected by KASAN:<br /> <br /> BUG: KASAN: slab-out-of-bounds in btrfs_qgroup_inherit+0x42e/0x2e20 fs/btrfs/qgroup.c:3277<br /> Read of size 8 at addr ffff88814628ca50 by task syz-executor318/5171<br /> <br /> CPU: 0 PID: 5171 Comm: syz-executor318 Not tainted 6.10.0-rc2-syzkaller-00010-g2ab795141095 #0<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024<br /> Call Trace:<br /> <br /> __dump_stack lib/dump_stack.c:88 [inline]<br /> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114<br /> print_address_description mm/kasan/report.c:377 [inline]<br /> print_report+0x169/0x550 mm/kasan/report.c:488<br /> kasan_report+0x143/0x180 mm/kasan/report.c:601<br /> btrfs_qgroup_inherit+0x42e/0x2e20 fs/btrfs/qgroup.c:3277<br /> create_pending_snapshot+0x1359/0x29b0 fs/btrfs/transaction.c:1854<br /> create_pending_snapshots+0x195/0x1d0 fs/btrfs/transaction.c:1922<br /> btrfs_commit_transaction+0xf20/0x3740 fs/btrfs/transaction.c:2382<br /> create_snapshot+0x6a1/0x9e0 fs/btrfs/ioctl.c:875<br /> btrfs_mksubvol+0x58f/0x710 fs/btrfs/ioctl.c:1029<br /> btrfs_mksnapshot+0xb5/0xf0 fs/btrfs/ioctl.c:1075<br /> __btrfs_ioctl_snap_create+0x387/0x4b0 fs/btrfs/ioctl.c:1340<br /> btrfs_ioctl_snap_create_v2+0x1f2/0x3a0 fs/btrfs/ioctl.c:1422<br /> btrfs_ioctl+0x99e/0xc60<br /> vfs_ioctl fs/ioctl.c:51 [inline]<br /> __do_sys_ioctl fs/ioctl.c:907 [inline]<br /> __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893<br /> do_syscall_x64 arch/x86/entry/common.c:52 [inline]<br /> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83<br /> entry_SYSCALL_64_after_hwframe+0x77/0x7f<br /> RIP: 0033:0x7fcbf1992509<br /> RSP: 002b:00007fcbf1928218 EFLAGS: 00000246 ORIG_RAX: 0000000000000010<br /> RAX: ffffffffffffffda RBX: 00007fcbf1a1f618 RCX: 00007fcbf1992509<br /> RDX: 0000000020000280 RSI: 0000000050009417 RDI: 0000000000000003<br /> RBP: 00007fcbf1a1f610 R08: 00007ffea1298e97 R09: 0000000000000000<br /> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcbf19eb660<br /> R13: 00000000200002b8 R14: 00007fcbf19e60c0 R15: 0030656c69662f2e<br /> <br /> <br /> And it also pinned it down to commit b5357cb268c4 ("btrfs: qgroup: do not<br /> check qgroup inherit if qgroup is disabled").<br /> <br /> [CAUSE]<br /> That offending commit skips the whole qgroup inherit check if qgroup is<br /> not enabled.<br /> <br /> But that also skips the very basic checks like<br /> num_ref_copies/num_excl_copies and the structure size checks.<br /> <br /> Meaning if a qgroup enable/disable race is happening at the background,<br /> and we pass a btrfs_qgroup_inherit structure when the qgroup is<br /> disabled, the check would be completely skipped.<br /> <br /> Then at the time of transaction commitment, qgroup is re-enabled and<br /> btrfs_qgroup_inherit() is going to use the incorrect structure and<br /> causing the above KASAN error.<br /> <br /> [FIX]<br /> Make btrfs_qgroup_check_inherit() only skip the source qgroup checks.<br /> So that even if invalid btrfs_qgroup_inherit structure is passed in, we<br /> can still reject invalid ones no matter if qgroup is enabled or not.<br /> <br /> Furthermore we do already have an extra safety inside<br /> btrfs_qgroup_inherit(), which would just ignore invalid qgroup sources,<br /> so even if we only skip the qgroup source check we&amp;#39;re still safe.