Olivier Certner
c3d2b68c69
In system calls changing process credentials, on RACCT, calls to racct_proc_ucred_changed() must be issued on the new credentials. Currently, this is done after the new credentials have been installed on the process via proc_set_cred() or proc_set_cred_enforce_proc_lim(), which modifies 'p_ucred'. Only the process lock guarantees that the new credentials pointed to by 'p_ucred' cannot themselves be concurrently modified, which would cause their 'struct ucred' to potentially lose its last reference from the process before the call to racct_proc_ucred_changed(), which needs one. For better code understandability and to avoid errors in future modifications, stop relying on proc_set_cred*() storing the passed 'struct ucred' in the process 'p_ucred' and on the process lock to avoid the reference taken by proc_set_cred*() to vanish. Instead, ensure that a reference is held when racct_proc_ucred_changed() is called. As racct_proc_ucred_changed() is actually passed explicit pointers to the old and new credentials, there is in fact no need to call it after proc_set_cred(). Instead, call it before proc_set_cred() and its taking over the reference. Since setcred() uses proc_set_cred_enforce_proc_lim(), which can fail, instead of proc_set_cred(), we instead take an additional reference with crhold(). Indeed, racct_proc_ucred_changed() should update resource accounting only if proc_set_cred_enforce_proc_lim() succeeds (an alternative would be to call it in advance and then in case of failure of the latter to call it again in order to backpedal the updated accounting, but we don't see a compelling reason to do that instead of taking an additional reference). While here, add to the documentation of proc_set_cred_enforce_proc_lim() that it does not take over the credentials reference in case of failure. While here, in racct_proc_ucred_changed()'s herald comment, add the precise condition in which this function must be called. No functional change intended. Reviewed by: kib MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D53563
FreeBSD Source:
This is the top level of the FreeBSD source directory.
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory. Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7), config(8), FreeBSD handbook on building userland, and Handbook for kernels for more information, including setting make(1) variables.
For information on the CPU architectures and platforms supported by FreeBSD, see the FreeBSD website's Platforms page.
For official FreeBSD bootable images, see the release page.
Source Roadmap:
| Directory | Description |
|---|---|
| bin | System/user commands. |
| cddl | Various commands and libraries under the Common Development and Distribution License. |
| contrib | Packages contributed by 3rd parties. |
| crypto | Cryptography stuff (see crypto/README). |
| etc | Template files for /etc. |
| gnu | Commands and libraries under the GNU General Public License (GPL) or Lesser General Public License (LGPL). Please see gnu/COPYING and gnu/COPYING.LIB for more information. |
| include | System include files. |
| kerberos5 | Kerberos5 (Heimdal) package. |
| lib | System libraries. |
| libexec | System daemons. |
| release | Release building Makefile & associated tools. |
| rescue | Build system for statically linked /rescue utilities. |
| sbin | System commands. |
| secure | Cryptographic libraries and commands. |
| share | Shared resources. |
| stand | Boot loader sources. |
| sys | Kernel sources (see sys/README.md). |
| targets | Support for experimental DIRDEPS_BUILD |
| tests | Regression tests which can be run by Kyua. See tests/README for additional information. |
| tools | Utilities for regression testing and miscellaneous tasks. |
| usr.bin | User commands. |
| usr.sbin | System administration commands. |
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see FreeBSD Handbook.