ocontext_to_sid(9)

📦 version 7.3.1, in nixpkgs unstable

💅 ocontext_to_sid(9) — like, the SELinux kernel API manual bestie ✨

okay so welcome to the ocontext_to_sid(9) page, straight out of the Kernel API Manual 🎀 this is the one that teaches you how to get a SID out of an ocontext without everything catching fire. stay with me, it's actually so good.

✨ NAME ✨

ocontext_to_sid — the helper that safely gets a sid for an ocontext 🫶 yes "safely" is doing a lot of work in that sentence and we love her for it.

✨ SYNOPSIS ✨

int ocontext_to_sid (struct sidtab *sidtab , struct ocontext *c , size_t
index , u32 *out_sid );

look at that signature. so clean. so many arguments. she's giving function-prototype realness 💅

✨ ARGUMENTS ✨

  • sidtab — the SID table 🌸 that's the big book of SIDs, you're working inside her.
  • c — the ocontext structure 🦋 the actual context thing you're pulling a SID out of.
  • index — index of the context entry 🔥 and heads up, it's literally 0 or 1, that's the whole range, no in-between.
  • out_sid — pointer to the resulting SID value ⭐ this is where the answer lands. pointer. so you gotta give her somewhere to write.

✨ DESCRIPTION ✨

okay so here's the vibe 👑 for all ocontexts except OCON_ISID, the SID fields are populated on-demand, like, when they're needed. not before. she's not doing extra work for nobody 💀

and because updating the SID value is an SMP-sensitive operation, you must use this helper to do that safely. no cap. do not go around it, do not do it yourself in a corner, use the helper 🙏

WARNING ⚠️ this function may return -ESTALE, which means the caller must retry the operation after re-acquiring the policy pointer! like, actually re-acquire it. don't just loop and hope 😭 it's telling you the policy pointer situation changed, so go get it again and then try once more.

the way this is genuinely just "here's a safe helper, also please handle -ESTALE" — iconic, honestly.

✨ SEE ALSO ✨

literally the whole security crew, all gathered in one place 🫶 and the kernel file she lives in: ./security/selinux/ss/services.c

like, read them. all of them. iykyk 💜

and that's the page, bestie! 💖 this little legend lives over in ./security/selinux/ss, and the version we're looking at is dated October 2026 🌈 go forth, get your SIDs, respect the -ESTALE, slay ✨🎀

📦 where this page comes from