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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] <TASK>
[ 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:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer: Getting started with kernel development * Academic Researcher: Studying kernel internals and architecture * Security Expert: Hardening and vulnerability analysis * Backport/Maintenance Engineer: Maintaining stable kernels * System Administrator: Configuring and troubleshooting * Maintainer: Leading subsystems and reviewing patches * Hardware Vendor: Writing drivers for new hardware * Distribution Maintainer: Packaging kernels for distros * AI Coding Assistant: LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. 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