{"id":"DEBIAN-CVE-2022-49783","details":"In the Linux kernel, the following vulnerability has been resolved:  x86/fpu: Drop fpregs lock before inheriting FPU permissions  Mike Galbraith reported the following against an old fork of preempt-rt but the same issue also applies to the current preempt-rt tree.     BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46    in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: systemd    preempt_count: 1, expected: 0    RCU nest depth: 0, expected: 0    Preemption disabled at:    fpu_clone    CPU: 6 PID: 1 Comm: systemd Tainted: G            E       (unreleased)    Call Trace:     \u003cTASK\u003e     dump_stack_lvl     ? fpu_clone     __might_resched     rt_spin_lock     fpu_clone     ? copy_thread     ? copy_process     ? shmem_alloc_inode     ? kmem_cache_alloc     ? kernel_clone     ? __do_sys_clone     ? do_syscall_64     ? __x64_sys_rt_sigprocmask     ? syscall_exit_to_user_mode     ? do_syscall_64     ? syscall_exit_to_user_mode     ? do_syscall_64     ? syscall_exit_to_user_mode     ? do_syscall_64     ? exc_page_fault     ? entry_SYSCALL_64_after_hwframe     \u003c/TASK\u003e  Mike says:    The splat comes from fpu_inherit_perms() being called under fpregs_lock(),   and us reaching the spin_lock_irq() therein due to fpu_state_size_dynamic()   returning true despite static key __fpu_state_size_dynamic having never   been enabled.  Mike's assessment looks correct. fpregs_lock on a PREEMPT_RT kernel disables preemption so calling spin_lock_irq() in fpu_inherit_perms() is unsafe. This problem exists since commit    9e798e9aa14c (\"x86/fpu: Prepare fpu_clone() for dynamically enabled features\").  Even though the original bug report should not have enabled the paths at all, the bug still exists.  fpregs_lock is necessary when editing the FPU registers or a task's FP state but it is not necessary for fpu_inherit_perms(). The only write of any FP state in fpu_inherit_perms() is for the new child which is not running yet and cannot context switch or be borrowed by a kernel thread yet. Hence, fpregs_lock is not protecting anything in the new child until clone() completes and can be dropped earlier. The siglock still needs to be acquired by fpu_inherit_perms() as the read of the parent's permissions has to be serialised.    [ bp: Cleanup splat. ]","modified":"2026-08-27T23:04:30.486073595Z","published":"2025-05-01T15:16:01.510Z","upstream":["CVE-2022-49783"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2022-49783"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.0.10-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49783.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.0.10-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49783.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.0.10-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2022-49783.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}