cap_task_prctl(9)

💅 cap_task_prctl(9) — the Kernel API Manual, bestie edition 🎀

okay so welcome to cap_task_prctl(9) from the Kernel API Manual — yes, we're reading kernel docs together, this is our bonding era ✨

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🌸 NAME 🌸

cap_task_prctl — the function that implements process control stuff for this security module, no cap 🧢

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✨ SYNOPSIS ✨

int cap_task_prctl (int option , unsigned long arg2 , unsigned long arg3
, unsigned long arg4 , unsigned long arg5 );

like... look at all those unsigned longs. she's thorough. she's committed. we respect her 💜

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🦋 ARGUMENTS 🦋

• option — the process control function that's being requested, iykyk 👑
• arg2 — the argument data for this function 🍓
• arg3 — the argument data for this function 🍓
• arg4 — the argument data for this function 🍓
• arg5 — the argument data for this function 🍓

(not me listing the same description four times 😭 but that's what the page says and I am nothing if not faithful 💀)

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🔥 DESCRIPTION 🔥

so basically, this lets process control functions (sys_prctl) alter capabilities. that's the main character energy right there 💅

she may also deny access to other functions that aren't otherwise implemented here — yes, she can gatekeep, and honestly? she's earned it. periodt.

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🌈 RETURN 🌈

• 0 or a positive value (+ve) on success — slay 🫶
• -ENOSYS if this function is not implemented here — the "not me, ask someone else" vibe 🙈
• other negative (-ve) values on error — it's giving "something went wrong" 💀

important little aside: if -ENOSYS gets returned, then sys_prctl and other LSM modules will consider performing the function themselves. so it's not a hard no, it's a "you go ahead, girl" 💖

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⭐ SEE ALSO ⭐

Kernel file ./security/commoncap.c, plus the whole friend group: cap_capable_helper(9), cap_capable(9), cap_settime(9), cap_ptrace_access_check(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_vm_enough_memory(9), cap_mmap_addr(9) — that's the entire squad, go say hi 🦋💜

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k bye bestie, mwah 💋

this iconic little page lives in ./security, drop date October 2026, and it's the cap_task_prctl(9) entry — go forth and prctl responsibly 🎀✨