security_transition_sid(9)

📦 version 7.3.1, in nixpkgs unstable

💅 security_transition_sid(9) — like, the Kernel API Manual era 🎀

okay so bestie, welcome to the glow-up era of SELinux SID math ✨ this one lives in the Kernel API Manual and it's honestly so iconic of it.

🌸 NAME 🌸

security_transition_sid — compute the SID for a new subject/object, no cap 💅

✨ SYNOPSIS ✨

int security_transition_sid (u32 ssid , u32 tsid , u16 tclass , const
struct qstr *qstr , u32 *out_sid );

like, five args, all vibes, we love to see it 🫶

🎀 ARGUMENTS 🎀

  • ssid — the source security identifier 💖 (where we're coming from, bestie)
  • tsid — the target security identifier ✨ (where we're going)
  • tclass — the target security class 🎯 (the category of the whole situation)
  • qstr — object name 🌸 (yes, the actual name-name)
  • out_sid — security identifier for the new subject/object 👑 (this is where the answer goes, it's giving output parameter energy)

🦋 DESCRIPTION 🦋

So here's the tea 🍓: security_transition_sid computes a SID to use for labeling a new subject or object in the class tclass, based on a SID pair — (ssid, tsid). That's it, that's the whole job, and it does it flawlessly.

Return values, and pay attention because this is the part people miss 😭:

  • returns -EINVAL if any of the parameters are invalid 🙈
  • returns -ENOMEM if insufficient memory is available 💀 (no memory, no SID, that's the rule)
  • returns 0 if the new SID was computed successfully ✅ slay
fr fr: check your return value. 0 is the win, the negatives are the not-wins, and you literally cannot tell which without looking. main character error handling only 💅

💜 SEE ALSO 💜

Kernel file ./security/selinux/ss/services.c — that's the source file, go read it if you want the real lore 📖

and the whole friend group of related calls, all in (9) section, all iconic in their own way 🌈:

💫 okay that's the whole page, ty for coming to my TED talk 💫

<cute sign-off>mwah 💋 this masterpiece comes from ./security/selinux/ss, dated October 2026 — cover the security_transition_sid(9) page in your journal and stan 🎀</cute sign-off>

📦 where this page comes from