__begin_cred_crit_section(9)

✨ __begin_cred_crit_section ✨

okay bestie, buckle up 💖 this one lives in the Kernel API Manual, and it's giving "lowkey serious kernel business but make it cute." It's all about kicking off a crit section on @cred's confining label, and honestly? iconic behavior. 🎀

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🌸 SYNOPSIS 🌸

struct aa_label * __begin_cred_crit_section (const struct cred *cred ,
bool *needput );

Like, that's the whole vibe. Struct pointer in, bool pointer out, chaos managed. 💅

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🦋 ARGUMENTS 🦋

• cred — current's cred, and we're starting a crit section on its label. That's the whole job, no cap. ✨
• needput — this one's a little messenger 🫶 it stores whether the label needs to be put when you're ending the crit section. Very "note to self" energy.

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👑 RETURN 👑

You get back the up to date confining label, OR the ns unconfined label — either way it's NOT NULL, so no sad little empty return values here, periodt. 🔥

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💜 DESCRIPTION 💜

First thing's first: it's safe to call inside locks. Slay. 🧚

The returned reference must be put with __end_cred_crit_section. And listen — this must NOT be used if the task cred could be updated within the critical section between __begin_cred_crit_section .. __end_cred_crit_section. Like, literally do not, bestie. 💀 That's the vibe check and it fails.

So what even is the crit section? It's an optimization to avoid having to get and put the newest version of the label. While the cred won't change — and hence the label it contains won't change — the newest version of the label totally can. During the crit section, the newest versions of the label will be used until the end of the crit section. It's giving "we'll catch up at the end, bestie." 🌈

If the label has not been updated at the start of the crit section, no refcount is taken — the cred's refcount is enough to hold the label for the duration of the crit section. Efficiency queen 👑✨

If the label has been updated, then a refcount will be taken and the newest version of the label will be returned. Now, while the cred label and the returned label could be compared at the end of the crit section, needput is used instead — because it allows better optimization by the compiler and the processor's speculative execution. The way that compiler eats this up, honestly obsessed. 🔥

💅 fr fr: this is the whole page, no cap — every option-free, flag-free, argument-having detail is right here.

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🔗 SEE ALSO 🔗

• Kernel file ./security/apparmor/include/cred.h 🎀
• aa_get_newest_cred_label(9)
• aa_current_raw_label(9)
• aa_get_current_label(9)
• __end_cred_crit_section(9)
• __end_current_label_crit_section(9)
• end_current_label_crit_section(9)
• __begin_current_label_crit_section(9)
• begin_current_label_crit_section(9)

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and that's the page, bestie! 🫶 this little masterpiece comes to you from ./security/apparmor/include, dated October 2026 — go off, AppArmor directory, we love to see it. 💖✨🎀