syscall_user_dispatch: Add kernel.syscall_user_dispatch sysctl

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Add a matching sysctl to go with CONFIG_SYSCALL_USER_DISPATCH.

kernel.syscall_user_dispatch (default 1 - allow) controls whether
userspace may arm syscall user dispatch (both via prctl and ptrace).

Disarming is always permitted - same semantics as comparable knobs.

Disabling while a task has armed syscall user dispatch does not
cause it to become inactive - instead it remains active until the
user attempts to disable/re-enable via prctl or ptrace.  On the
next attempt to re-enable, the prctl/ptrace call fails gracefully.

The alternative would cause programs translating non-linux syscalls
to interpret those syscalls as linux syscalls, resulting in undefined
userland behavior.

Signed-off-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260706140020.873735-3-gourry@gourry.net

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Gregory Price 2026-07-06 10:00:19 -04:00 • committed by Thomas Gleixner

parent ee935e8dc7

commit 5b6e32ba7b

2 changed files with 48 additions and 7 deletions

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17

Documentation/admin-guide/sysctl/kernel.rst

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38

kernel/entry/syscall_user_dispatch.c

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