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seccomp_notify_alloc(3) — Linux manual page

seccomp_notify_alloc(3)  libseccomp Documentationseccomp_notify_alloc(3)

NAME        top

       seccomp_notify_alloc, seccomp_notify_free, seccomp_notify_receive,       seccomp_notify_respond, seccomp_notify_id_valid, seccomp_notify_fd       - Manage seccomp notifications

SYNOPSIS        top

#include <seccomp.h>int seccomp_notify_alloc(struct seccomp_notif **req, struct seccomp_notif_resp **resp)void seccomp_notify_free(struct seccomp_notif *req, struct seccomp_notif_resp *resp)int seccomp_notify_receive(intfd, struct seccomp_notif *req)int seccomp_notify_respond(intfd, struct seccomp_notif_resp *resp)int seccomp_notify_id_valid(intfd, uint64_tid)int seccomp_notify_fd(const scmp_filter_ctxctx)       Link with-lseccomp.

DESCRIPTION        top

       Theseccomp_notify_alloc() function dynamically allocates enough       memory for a seccomp notification and response. Note that one       should always use these functions and not depend on the structure       sizes in headers, since the size can vary depending on the kernel       version. This function takes care to ask the kernel how big each       structure should be, and allocates the right amount of memory. Theseccomp_notify_free() function frees memory allocated byseccomp_notify_alloc().       Theseccomp_notify_receive() function receives a notification from       a seccomp notify fd (obtained fromseccomp_notify_fd()).       Theseccomp_notify_respond() function sends a response to a       particular notification. The id field should be the same as the id       from the request, so that the kernel knows which request this       response corresponds to.       Theseccomp_notify_id_valid() function checks to see if the       syscall from a particular notification request is still valid,       i.e. if the task is still alive. See NOTES below for details on       race conditions.       Theseccomp_notify_fd() returns the notification fd of a filter       after it has been loaded.

RETURN VALUE        top

       Theseccomp_notify_fd() returns the notification fd of the loaded       filter, -1 if a notification fd has not yet been created, and       -EINVAL if the filter context is invalid.       Theseccomp_notify_id_valid() returns 0 if the id is valid, and       -ENOENT if it is not.       Theseccomp_notify_alloc(),seccomp_notify_receive(), andseccomp_notify_respond() functions return zero on success,  or one       of the following error codes on failure:-ECANCELED              There was a system failure beyond the control of the              library, check theerrno value for more information.-EFAULT              Internal libseccomp failure.-ENOMEM              The library was unable to allocate enough memory.-EOPNOTSUPP              The library doesn't support the particular operation.

NOTES        top

       Care should be taken to avoid two different time of check/time of       use errors.  First, after opening any resources relevant to the       pid for a notification (e.g.  /proc/pid/mem for reading tracee       memory to make policy decisions), applications should callseccomp_notify_id_valid() to make sure that the resources the       application has opened correspond to the right pid, i.e. that the       pid didn't die and a different task take its place.       Second, the classic time of check/time of use issue with seccomp       memory should also be avoided: applications should copy any memory       they wish to use to make decisions from the tracee into its own       address space before applying any policy decisions, since a multi-       threaded tracee may edit the memory at any time, including after       it's used to make a policy decision.       A complete example of how to avoid these two races is available in       the Linux Kernel source tree at/samples/seccomp/user-trap.c.

AUTHOR        top

       Tycho Andersen <tycho@tycho.ws>

COLOPHON        top

       This page is part of thelibseccomp (high-level API to the Linux       Kernel's seccomp filter) project.  Information about the project       can be found at ⟨https://github.com/seccomp/libseccomp⟩.  If you       have a bug report for this manual page, see       ⟨https://groups.google.com/d/forum/libseccomp⟩.  This page was       obtained from the project's upstream Git repository       ⟨https://github.com/seccomp/libseccomp⟩ on 2025-08-11.  (At that       time, the date of the most recent commit that was found in the       repository was 2025-05-09.)  If you discover any rendering       problems in this HTML version of the page, or you believe there is       a better or more up-to-date source for the page, or you have       corrections or improvements to the information in this COLOPHON       (which isnot part of the original manual page), send a mail to       man-pages@man7.orgtycho@tycho.ws                 30 May 2020seccomp_notify_alloc(3)

Pages that refer to this page:seccomp_init(3), seccomp_rule_add(3)

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