linux-next.git/kernel/fork.c, branch stable

sched/cache: Introduce task_struct->sched_cache_grp to fix UAF

2026-09-22T08:50:43+00:00

Add a sched_cache_grp pointer to task_struct so that scheduler code can access the cache group directly via the task, without going through mm->sched_cache_grp. This decouples the scheduler's hot-path accesses from the mm_struct. Each task holds its own refcount on the sched_cache_group, separate from the reference held by its mm_struct. The reference is acquired in copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm(). This fixes the use-after-free when account_mm_sched() reaches the group through a task whose mm is being switched, as reported by Hyunwoo: https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/ Convert all scheduler code in fair.c and exit.c to use p->sched_cache_grp instead of p->mm->sched_cache_grp. Keep the fork/exec/exit reference management out of the generic mm paths: add sched_cache_fork(), sched_cache_fork_cleanup(), sched_cache_exec_mmap() and sched_cache_exit_mm() in kernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE), so fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper instead of open-coding the refcounting under #ifdef. Also add sched_cache_group_get() and task_cache_group_get(). Fixes: df0d98475954 ("sched/cache: Introduce infrastructure for cache-aware load balancing") Closes: https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/ Closes: https://lore.kernel.org/all/343a7e07-7fad-4979-9c9b-82ec038c293c@linux.dev/ Reported-by: Hyunwoo Kim Reported-by: Zenghui Yu (Huawei) Co-developed-by: Chen Yu Signed-off-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Cc: #7.2.x Link: https://patch.msgid.link/ae7081dc54736bf115215f9867abb2711a7403fb.1790035273.git.tim.c.chen@linux.intel.com

futex: Also allocate private hash on vfork()

2026-09-16T12:20:41+00:00

As Jann demonstrated, it is entirely feasible to access the mm through vfork(). Therefore we need to allocate a private hash on vfork() as well as any other CLONE_VM user. Specifically, it must be avoided to have (private) futex waiters before allocating the private hash. Fixes: ee9dce44362b ("futex: Drop CLONE_THREAD requirement for private default hash alloc") Reported-by: Jann Horn Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260911090447.GT788244@noisy.programming.kicks-ass.net

ftrace: fork: Initialize function graph state before copy_exec_state()

2026-09-11T17:33:54+00:00

dup_task_struct() copies the parent's task_struct, including ret_stack. ftrace_graph_init_task() clears the copied function graph state, but it currently runs after copy_exec_state(). For non-CLONE_VM forks, copy_exec_state() allocates a new task_exec_state. If that allocation fails, copy_process() reaches bad_fork_free and free_task() calls ftrace_graph_exit_task(). Since the child still carries the parent's ret_stack pointer, the unwind frees the parent's active function graph return stack. The parent subsequently accesses freed memory from function_graph_enter_regs(). KASAN reports: [ 22.190920] ================================================================== [ 22.195899] BUG: KASAN: slab-use-after-free in function_graph_enter_regs+0xa76/0xb90 [ 22.200747] Write of size 8 at addr ff110000054dc0a8 by task repro/1 [ 22.205134] [ 22.210770] CPU: 0 UID: 0 PID: 1 Comm: repro Not tainted 7.2.0-07732-g9328b3b03bdc-dirty #3 PREEMPT(lazy) [ 22.212576] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 22.213750] Call Trace: [ 22.215271] [ 22.216242] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.217774] dump_stack_lvl+0x4e/0x70 [ 22.220531] print_report+0x157/0x4b4 [ 22.223202] ? fixup_red_left+0x9/0x30 [ 22.224407] ? complete_report_info+0x83/0x110 [ 22.226679] ? function_graph_enter_regs+0xa76/0xb90 [ 22.228084] kasan_report+0xce/0x100 [ 22.230109] ? function_graph_enter_regs+0xa76/0xb90 [ 22.232860] ? stack_trace_save+0x4/0xd0 [ 22.234156] function_graph_enter_regs+0xa76/0xb90 [ 22.236090] ? kasan_save_stack+0x30/0x50 [ 22.237752] ? __pfx_function_graph_enter_regs+0x10/0x10 [ 22.238694] ? ring_buffer_lock_reserve+0x345/0xf80 [ 22.239628] ? stack_trace_save+0x4/0xd0 [ 22.242121] ? stack_trace_save+0x4/0xd0 [ 22.243588] ftrace_graph_func+0xda/0x160 [ 22.245362] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.246520] 0xffffffffa0000095 [ 22.250528] ? stack_trace_save+0x9/0xd0 [ 22.251757] ? ring_buffer_unlock_commit+0x11d/0x5c0 [ 22.253152] stack_trace_save+0x9/0xd0 [ 22.254264] kasan_save_stack+0x30/0x50 [ 22.273631] kasan_save_track+0x14/0x30 [ 22.276763] kasan_save_free_info+0x3b/0x70 [ 22.278296] __kasan_slab_free+0x43/0x70 [ 22.280157] kmem_cache_free+0xbf/0x3b0 [ 22.282963] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.284001] free_task+0xa2/0x160 [ 22.285699] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.286752] copy_process+0x2aae/0x7bc0 Initialize the child function graph state immediately after dup_task_struct(), before the first fallible operation. Cc: stable@vger.kernel.org Fixes: 6b1c66c9cca9 ("exec_state: relocate dumpable information") Reviewed-by: Bradley Morgan Link: https://patch.msgid.link/20260822195321.962383-2-Jeremy.Jean@oss.cyber.gouv.fr Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Signed-off-by: Steven Rostedt

Merge tag 'mm-nonmm-stable-2026-08-22-16-57' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-23T15:07:11+00:00

Pull non-MM updates from Andrew Morton: - "ocfs2/dlm: bound peer-controlled lengths in the o2dlm" (Bryam Vargas) Validate and bound all input lengths and count fields in the o2dlm migration and recovery receive handlers to prevent memory corruption and kernel panics from malformed cluster messages - "ocfs2: validate xattr entry bounds" (Cen Zhang) Validate OCFS2 extended attribute entry name and value bounds during metadata reads to prevent out-of-range memory accesses during retrieval or listing operations. - "taskstats: fix cgroupstats invalid fd handling and add selftests" (Yiyang Chen) Return -EBADF when cgroupstats receives an invalid file descriptor to prevent caller hangs and misleading success ACKs. Add a kselftest to validate valid cgroup v1 queries and verify proper error handling across different Netlink flag combinations. - "misc lib/raid/ improvements v2" (Christoph Hellwig) Improve benchmark-based algorithm selection for the XOR and RAID6 libraries, add KUnit benchmark tests, and cleanup minor implementation details. - "ocfs2: cluster: o2hb_region_pin() fixes" (Joseph Qi) Fix sleeping-in-atomic, lock order inversion and error-path cleanup bugs in o2hb_region_pin() by releasing o2hb_live_lock across sleeping configfs_depend_item() calls and using unlocked variants from callback context. Ensure failed pin attempts properly decrement user counts and unpin partially initialized heartbeat regions to prevent memory leaks and unprotected states. - "lib/ucs2_string.c: fix out-of-bounds read in ucs2_strnlen()" (Vincent Mailhol) Fix an off-by-one which could cause an out-of-bounds read. - "ocfs2: harden heartbeat teardown races" (Cen Zhang) Fix two OCFS2 heartbeat/o2net teardown races found by KASAN. - "taskstats: tidy up the cpumask command path" *Bradley Morgan) make two small cleanups in kernel/taskstats.c. - "ocfs2: validate active orphan slots during inode read" (ZhengYuan Huang) Validate active ordinary and append-DIO orphan slots read from OCFS2 dinodes at the metadata boundary to prevent corrupted slot indices from causing out-of-bounds array accesses. - "ocfs2: bound-check both readdir re-validation scans" (Zhan Xusheng) Enforce strict boundary checks on directory entry record lengths and offset calculations during OCFS2 directory re-scans to prevent out-of-bounds memory reads and directory position corruption. * tag 'mm-nonmm-stable-2026-08-22-16-57' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (95 commits) mailmap: fix bouncing address for Taniya Das ocfs2: bound-check dir entries in the inline-data re-validation scan ocfs2: bound-check dir entries in the readdir re-validation scan squashfs: avoid thundering-herd cache wakeups prctl: fix PR_SET_MM_AUXV losing the forced AT_NULL terminator mailmap: update email address for Linfeng Sun lib/interval_tree: fix allocation warning messages checkpatch: add NOKPROBE_SYMBOL to the whitelist of lines that can occur immediately after functions Squashfs: check block offset is not negative signal: factor out the kernel reserved si_code check ocfs2: fix readdir position truncation on 32-bit kernels ocfs2: fix cached cluster count after suballocator reclaim ocfs2: fix circular locking dependency in ocfs2_init_acl() ocfs2: validate DIO orphan slot during inode read ocfs2: validate orphan slot during inode read selftests/prctl: fix non-anonymous VMA mapping in set-anon-vma-name test MAINTAINERS: add IRC and patchwork for LTP include/linux/list.h: mark list_add and __list_add as __always_inline tools/mm: prevent page_owner_sort from truncating input hung_task: update DETECT_HUNG_TASK_BLOCKER Kconfig help ...

Merge tag 'locking-urgent-2026-08-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2026-08-22T23:29:20+00:00

Pull futex fixes from Ingo Molnar: - Enforce that the private futex owner shares the mm when attaching (Kyle Zeng, Thomas Gleixner) - Fix race on the initial mm->futex.phash.ref allocation (Hyunwoo Kim) - Fix might_sleep() warning in futex_pivot_pending() (Peter Zijlstra) * tag 'locking-urgent-2026-08-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: futex: Fix might_sleep() warning in futex_pivot_pending() futex: Fix race on the initial mm->futex.phash.ref allocation futex: Clean up the redundant exit/exec functions futex/pi: Plug private futex exec() race futex: Sanitize and document task_struct::futex::state transitions futex/pi: Reject cross-mm private futex owners

Merge tag 'smp-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2026-08-18T22:29:53+00:00

Pull SMP core updates from Thomas Gleixner: - Reduce the preemption disabled sections in smp_call_function*(). The various smp call functions keep preemption disabled accross the full operation which includes the wait for completion. Especially the latter can take some time when one of the target CPUs is not immediately responding to the IPI, which can result in large latency spikes. To improve this provide a per task CPU mask to track the CPUs to wait for. That makes the information required for the wait task local and therefore allows to reenable preemption before the wait. While this comes with moderate extra memory cost this reduces SMP function call induced latency measured in a fleet for high priority tasks from ~17ms to ~1.5ms (~90%). - Reduce the overhead of the CSD debug code by replacing the heavy memory barriers with smp_store_release()/acquire() - Remove obsolute unused hotplug states * tag 'smp-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: scftorture: Remove preempt_disable() in scftorture_invoke_one() smp: Remove preempt_disable() from on_each_cpu_cond_mask() smp: Remove preempt_disable() from smp_call_function() smp: Enable preemption early in smp_call_function_many_cond() smp: Alloc percpu csd data in smpcfd_prepare_cpu() only once smp: Use task-local IPI cpumask in smp_call_function_many_cond() smp: Refactor remote CPU selection in smp_call_function_any() smp: Enable preemption early in smp_call_function_single() smp: Disable preemption explicitly in __csd_lock_wait() cpu/hotplug: Remove CPUHP_AP_ARM_CORESIGHT_CTI_STARTING smp: Use release stores for csd_lock_record() state

Merge tag 'perf-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2026-08-18T19:31:07+00:00

Pull performance events updates from Ingo Molnar: "uprobes updates: - Fix a category of bugs with optimized uprobes that can clobber the redzone area with call instruction storing return address on stack where user code may keep temporary data without adjusting RSP. Fix this by moving the optimized uprobes on top of 10-bytes NOP instruction, so we can squeeze another instruction to escape the redzone area before doing the call (Jiri Olsa, Andrii Nakryiko) - Switch uretprobes_srcu to SRCU-fast-updown, to improve performance (Puranjay Mohan) Intel CPU PMU driver updates: - Optimize ACR handling in match_prev_assignment() (Dapeng Mi) - Fix various PMU driver bugs and data leaks (Dapeng Mi) - Fix Intel PT stop/start with no update (Adrian Hunter) Intel uncore PMU driver updates: - Fix various uncore PMU setup robustness bugs (Zide Chen) AMD uncore PMU driver updates: - Add group validation (Sandipan Das) .. and misc fixes and updates by Dapeng Mi, Randy Dunlap and Zide Chen" * tag 'perf-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (42 commits) perf/x86: Optimize ACR handling in match_prev_assignment() perf/x86/intel: Fix intel_cap handling on hybrid PMUs perf/x86: Remove stale fixed counter helper and fix hybrid PMU access perf/x86/intel: Unwind cpuc state if PEBS buffer setup fails perf/x86: Guard intel_pmu_cpu_dead() against invalid hybrid PMU casts perf/x86: Free hybrid state on PMU init failure perf/x86: Unregister PMI handler on PMU init failure perf/x86/intel/pt: Fix stop/start with no update perf/x86/intel/pt: Use bitwise access for PERF_HES_STOPPED perf/x86/intel/pt: Factor out pt_config_enable() uprobes: Switch uretprobes_srcu to SRCU-fast-updown srcu: Add lock guard for srcu_fast_updown flavor perf/x86/intel/pt: Drop kernel-doc for deleted struct members perf/x86/amd/uncore: Add group validation selftests/bpf: Add tests for forked/cloned optimized uprobes selftests/bpf: Add tests for uprobe nop10 red zone clobbering selftests/bpf: Add reattach tests for uprobe syscall selftests/bpf: Change uprobe/usdt trigger bench code to use nop10 selftests/bpf: Change uprobe syscall tests to use nop10 selftests/bpf: Emit nop,nop10 instructions combo for x86_64 arch ...

Merge tag 'vfs-7.3-rc1.kthread' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-08-17T18:35:12+00:00

Pull kthread vfs updates from Christian Brauner: "This stops kernel threads from sharing filesystem state with userspace. This work is about 3 cycles old and has been in -next for about that time. When the kernel boots init_task creates PID 1 and then kthreadd. From that point every kthread and PID 1 share the same fs_struct. That is why pivot_root() has to rewrite the fs_struct of all kthreads. The rewriting exists so that kthreads can use init's filesystem state when they want to. It also means userspace can move the ground out from under the kernel. PID 1 now gets a completely separate fs_struct. All kthreads are anchored in a private SB_KERNMOUNT instance of nullfs that cannot be mounted on and cannot be used to follow other mounts. Userspace init can no longer affect kthread filesystem state and kthreads can no longer affect userspace fs state without explicit opting in to that. Path lookup from a kthread now fails by default. It makes it deliberately hard to offload security sensitive operations into init's filesystem state from a kthread. Places that legitimately need to look something up there opt in through the new scoped_with_init_fs() which temporarily overrides the caller's fs_struct with init's. usermodehelpers remain the only kernel tasks that genuinely share init's filesystem state, since they execute random binaries in the root filesystem (excellent...). The visible result is that /proc/2/root is a nullfs with an empty mountinfo while /proc/1/root is the real root" * tag 'vfs-7.3-rc1.kthread' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (26 commits) initramfs_test: use test init/exit hooks to override init fs fs: stop rewriting paths for PF_EXITING | PF_DUMPCORE fs: stop rewriting kthread fs structs fs: start all kthreads in nullfs nullfs: make nullfs multi-instance devtmpfs: create private mount namespace fs: add umh argument to struct kernel_clone_args fs: stop sharing fs_struct between init_task and pid 1 af_unix: use scoped_with_init_fs() for coredump socket lookup initramfs: use scoped_with_init_fs() for rootfs unpacking pnfs/blocklayout: use scoped_with_init_fs() for SCSI device lookup ksmbd: use scoped_with_init_fs() for VFS path operations ksmbd: use scoped_with_init_fs() for filesystem info path lookup ksmbd: use scoped_with_init_fs() for share path resolution fs: use scoped_with_init_fs() for kernel_read_file_from_path_initns() coredump: use scoped_with_init_fs() for coredump path resolution btrfs: use scoped_with_init_fs() for update_dev_time() scsi: target: use scoped_with_init_fs() for APTPL metadata scsi: target: use scoped_with_init_fs() for ALUA metadata crypto: ccp: use scoped_with_init_fs() for SEV file access ...

futex: Clean up the redundant exit/exec functions

2026-08-15T22:16:32+00:00

futex_exit_release() and futex_exec_release() are identical now. That means also exit_mm_release() and exec_mm_release() are identical. Consolidate the whole lot and remove the redundant copies. Signed-off-by: Thomas Gleixner Reviewed-by: Kyle Zeng Acked-by: Peter Zijlstra

kernel/fork: declare max_threads __read_mostly

2026-08-04T04:10:11+00:00

max_threads is initialized once by fork_init()->set_max_threads(), and thereafter is mostly read in hot path, such as copy_process(). The fact that it is mostly read and not written to makes it candidates for __read_mostly declarations. I have already tested on my machine(arm64,256core,kernel-7.1.3) with 'hackbench -P -l 500 -g 100/500/1000/2000' and the results show that there is an average of 13% improvement in performance. before patch: hackbench -g 100 500 1000 2000 1.094 4.651 13.305 36.322 after patch: hackbench -g 100 500 1000 2000 0.823 4.487 11.107 32.987 Above data are the average values obtained from multiple tests, and there was indeed some fluctuation in the data during the tests. Link: https://lore.kernel.org/20260707092354.465847-1-jansef.jian@hj-micro.com Signed-off-by: JianChunfu Reviewed-by: Lorenzo Stoakes Cc: Dietmar Eggemann Cc: Ingo Molnar Cc: Kees Cook Cc: Liam R. Howlett Cc: Peter Zijlstra Cc: Steven Rostedt Signed-off-by: Andrew Morton