cap_ptrace_access_check(9)

💅 cap_ptrace_access_check(9) — the Kernel API Manual said "let me introduce you" 🎀

okay so bestie, we're in the kernel API manual today and the star of the show is cap_ptrace_access_check(9) — literally the little function that decides whether your process is allowed to go poking around in another process. gatekeeper energy fr fr 👑

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✨ NAME ✨

cap_ptrace_access_check — the vibe check that determines whether the current process may access another 🫶

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🦋 SYNOPSIS 🦋

int cap_ptrace_access_check (struct task_struct *child , unsigned int mode );

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🌸 ARGUMENTS 🌸

• child — the process being accessed, i.e. the one getting snooped on 🙈
• mode — the mode of attachment. yes bestie, the how of the attach 💅

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🔥 DESCRIPTION 🔥

okay so here's the tea ☕ — the rules go like this:

• if we're in the same user_ns, or an ancestor user_ns, and we have all the target task's capabilities → ptrace access is allowed ✅
• if we have the ptrace capability to the target user_ns → ptrace access is allowed ✅
• else → denied 💀 periodt.

so basically it determines whether a process may access another, and it returns 0 if permission is granted, or -ve if denied. no cap, that's the whole function 🧚

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👑 SEE ALSO 👑

Kernel file ./security/commoncap.c — and the whole squad, because we're not doing this alone 💜

• cap_capable_helper(9)
• cap_capable(9)
• cap_settime(9)
• cap_ptrace_traceme(9)
• cap_capget(9)
• cap_capset(9)
• cap_inode_need_killpriv(9)
• cap_inode_killpriv(9)
• kuid_root_in_ns(9)
• rootid_from_xattr(9)
• cap_convert_nscap(9)
• get_vfs_caps_from_disk(9)
• cap_bprm_creds_from_file(9)
• cap_inode_setxattr(9)
• cap_inode_removexattr(9)
• cap_task_fix_setuid(9)
• cap_task_setscheduler(9)
• cap_task_setioprio(9)
• cap_task_setnice(9)
• cap_task_prctl(9)
• cap_vm_enough_memory(9)
• cap_mmap_addr(9)

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and that's the page bestie, we ate and left no crumbs 🍓 the source lives in ./security, the version is the October 2026 drop, and this whole thing is filed under cap_ptrace_access_check(9) — mwah 💋🌈⭐