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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/admin-guide/sysctl/fs.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/admin-guide/sysctl/fs.rst')
-rw-r--r-- | Documentation/admin-guide/sysctl/fs.rst | 334 |
1 files changed, 334 insertions, 0 deletions
diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst new file mode 100644 index 000000000..a321b84ec --- /dev/null +++ b/Documentation/admin-guide/sysctl/fs.rst @@ -0,0 +1,334 @@ +=============================== +Documentation for /proc/sys/fs/ +=============================== + +Copyright (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +Copyright (c) 2009, Shen Feng<shen@cn.fujitsu.com> + +For general info and legal blurb, please look in intro.rst. + +------------------------------------------------------------------------------ + +This file contains documentation for the sysctl files and directories +in ``/proc/sys/fs/``. + +The files in this directory can be used to tune and monitor +miscellaneous and general things in the operation of the Linux +kernel. Since some of the files *can* be used to screw up your +system, it is advisable to read both documentation and source +before actually making adjustments. + +1. /proc/sys/fs +=============== + +Currently, these files might (depending on your configuration) +show up in ``/proc/sys/fs``: + +.. contents:: :local: + + +aio-nr & aio-max-nr +------------------- + +``aio-nr`` shows the current system-wide number of asynchronous io +requests. ``aio-max-nr`` allows you to change the maximum value +``aio-nr`` can grow to. If ``aio-nr`` reaches ``aio-nr-max`` then +``io_setup`` will fail with ``EAGAIN``. Note that raising +``aio-max-nr`` does not result in the +pre-allocation or re-sizing of any kernel data structures. + + +dentry-state +------------ + +This file shows the values in ``struct dentry_stat``, as defined in +``linux/include/linux/dcache.h``:: + + struct dentry_stat_t dentry_stat { + int nr_dentry; + int nr_unused; + int age_limit; /* age in seconds */ + int want_pages; /* pages requested by system */ + int nr_negative; /* # of unused negative dentries */ + int dummy; /* Reserved for future use */ + }; + +Dentries are dynamically allocated and deallocated. + +``nr_dentry`` shows the total number of dentries allocated (active ++ unused). ``nr_unused shows`` the number of dentries that are not +actively used, but are saved in the LRU list for future reuse. + +``age_limit`` is the age in seconds after which dcache entries +can be reclaimed when memory is short and ``want_pages`` is +nonzero when ``shrink_dcache_pages()`` has been called and the +dcache isn't pruned yet. + +``nr_negative`` shows the number of unused dentries that are also +negative dentries which do not map to any files. Instead, +they help speeding up rejection of non-existing files provided +by the users. + + +file-max & file-nr +------------------ + +The value in ``file-max`` denotes the maximum number of file- +handles that the Linux kernel will allocate. When you get lots +of error messages about running out of file handles, you might +want to increase this limit. + +Historically,the kernel was able to allocate file handles +dynamically, but not to free them again. The three values in +``file-nr`` denote the number of allocated file handles, the number +of allocated but unused file handles, and the maximum number of +file handles. Linux 2.6 and later always reports 0 as the number of free +file handles -- this is not an error, it just means that the +number of allocated file handles exactly matches the number of +used file handles. + +Attempts to allocate more file descriptors than ``file-max`` are +reported with ``printk``, look for:: + + VFS: file-max limit <number> reached + +in the kernel logs. + + +inode-nr & inode-state +---------------------- + +As with file handles, the kernel allocates the inode structures +dynamically, but can't free them yet. + +The file ``inode-nr`` contains the first two items from +``inode-state``, so we'll skip to that file... + +``inode-state`` contains three actual numbers and four dummies. +The actual numbers are, in order of appearance, ``nr_inodes``, +``nr_free_inodes`` and ``preshrink``. + +``nr_inodes`` stands for the number of inodes the system has +allocated. + +``nr_free_inodes`` represents the number of free inodes (?) and +preshrink is nonzero when the +system needs to prune the inode list instead of allocating +more. + + +mount-max +--------- + +This denotes the maximum number of mounts that may exist +in a mount namespace. + + +nr_open +------- + +This denotes the maximum number of file-handles a process can +allocate. Default value is 1024*1024 (1048576) which should be +enough for most machines. Actual limit depends on ``RLIMIT_NOFILE`` +resource limit. + + +overflowgid & overflowuid +------------------------- + +Some filesystems only support 16-bit UIDs and GIDs, although in Linux +UIDs and GIDs are 32 bits. When one of these filesystems is mounted +with writes enabled, any UID or GID that would exceed 65535 is translated +to a fixed value before being written to disk. + +These sysctls allow you to change the value of the fixed UID and GID. +The default is 65534. + + +pipe-user-pages-hard +-------------------- + +Maximum total number of pages a non-privileged user may allocate for pipes. +Once this limit is reached, no new pipes may be allocated until usage goes +below the limit again. When set to 0, no limit is applied, which is the default +setting. + + +pipe-user-pages-soft +-------------------- + +Maximum total number of pages a non-privileged user may allocate for pipes +before the pipe size gets limited to a single page. Once this limit is reached, +new pipes will be limited to a single page in size for this user in order to +limit total memory usage, and trying to increase them using ``fcntl()`` will be +denied until usage goes below the limit again. The default value allows to +allocate up to 1024 pipes at their default size. When set to 0, no limit is +applied. + + +protected_fifos +--------------- + +The intent of this protection is to avoid unintentional writes to +an attacker-controlled FIFO, where a program expected to create a regular +file. + +When set to "0", writing to FIFOs is unrestricted. + +When set to "1" don't allow ``O_CREAT`` open on FIFOs that we don't own +in world writable sticky directories, unless they are owned by the +owner of the directory. + +When set to "2" it also applies to group writable sticky directories. + +This protection is based on the restrictions in Openwall. + + +protected_hardlinks +-------------------- + +A long-standing class of security issues is the hardlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like ``/tmp``. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given hardlink (i.e. a +root process follows a hardlink created by another user). Additionally, +on systems without separated partitions, this stops unauthorized users +from "pinning" vulnerable setuid/setgid files against being upgraded by +the administrator, or linking to special files. + +When set to "0", hardlink creation behavior is unrestricted. + +When set to "1" hardlinks cannot be created by users if they do not +already own the source file, or do not have read/write access to it. + +This protection is based on the restrictions in Openwall and grsecurity. + + +protected_regular +----------------- + +This protection is similar to `protected_fifos`_, but it +avoids writes to an attacker-controlled regular file, where a program +expected to create one. + +When set to "0", writing to regular files is unrestricted. + +When set to "1" don't allow ``O_CREAT`` open on regular files that we +don't own in world writable sticky directories, unless they are +owned by the owner of the directory. + +When set to "2" it also applies to group writable sticky directories. + + +protected_symlinks +------------------ + +A long-standing class of security issues is the symlink-based +time-of-check-time-of-use race, most commonly seen in world-writable +directories like ``/tmp``. The common method of exploitation of this flaw +is to cross privilege boundaries when following a given symlink (i.e. a +root process follows a symlink belonging to another user). For a likely +incomplete list of hundreds of examples across the years, please see: +https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp + +When set to "0", symlink following behavior is unrestricted. + +When set to "1" symlinks are permitted to be followed only when outside +a sticky world-writable directory, or when the uid of the symlink and +follower match, or when the directory owner matches the symlink's owner. + +This protection is based on the restrictions in Openwall and grsecurity. + + +suid_dumpable +------------- + +This value can be used to query and set the core dump mode for setuid +or otherwise protected/tainted binaries. The modes are + += ========== =============================================================== +0 (default) Traditional behaviour. Any process which has changed + privilege levels or is execute only will not be dumped. +1 (debug) All processes dump core when possible. The core dump is + owned by the current user and no security is applied. This is + intended for system debugging situations only. + Ptrace is unchecked. + This is insecure as it allows regular users to examine the + memory contents of privileged processes. +2 (suidsafe) Any binary which normally would not be dumped is dumped + anyway, but only if the ``core_pattern`` kernel sysctl (see + :ref:`Documentation/admin-guide/sysctl/kernel.rst <core_pattern>`) + is set to + either a pipe handler or a fully qualified path. (For more + details on this limitation, see CVE-2006-2451.) This mode is + appropriate when administrators are attempting to debug + problems in a normal environment, and either have a core dump + pipe handler that knows to treat privileged core dumps with + care, or specific directory defined for catching core dumps. + If a core dump happens without a pipe handler or fully + qualified path, a message will be emitted to syslog warning + about the lack of a correct setting. += ========== =============================================================== + + + +2. /proc/sys/fs/binfmt_misc +=========================== + +Documentation for the files in ``/proc/sys/fs/binfmt_misc`` is +in Documentation/admin-guide/binfmt-misc.rst. + + +3. /proc/sys/fs/mqueue - POSIX message queues filesystem +======================================================== + + +The "mqueue" filesystem provides the necessary kernel features to enable the +creation of a user space library that implements the POSIX message queues +API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System +Interfaces specification.) + +The "mqueue" filesystem contains values for determining/setting the +amount of resources used by the file system. + +``/proc/sys/fs/mqueue/queues_max`` is a read/write file for +setting/getting the maximum number of message queues allowed on the +system. + +``/proc/sys/fs/mqueue/msg_max`` is a read/write file for +setting/getting the maximum number of messages in a queue value. In +fact it is the limiting value for another (user) limit which is set in +``mq_open`` invocation. This attribute of a queue must be less than +or equal to ``msg_max``. + +``/proc/sys/fs/mqueue/msgsize_max`` is a read/write file for +setting/getting the maximum message size value (it is an attribute of +every message queue, set during its creation). + +``/proc/sys/fs/mqueue/msg_default`` is a read/write file for +setting/getting the default number of messages in a queue value if the +``attr`` parameter of ``mq_open(2)`` is ``NULL``. If it exceeds +``msg_max``, the default value is initialized to ``msg_max``. + +``/proc/sys/fs/mqueue/msgsize_default`` is a read/write file for +setting/getting the default message size value if the ``attr`` +parameter of ``mq_open(2)`` is ``NULL``. If it exceeds +``msgsize_max``, the default value is initialized to ``msgsize_max``. + +4. /proc/sys/fs/epoll - Configuration options for the epoll interface +===================================================================== + +This directory contains configuration options for the epoll(7) interface. + +max_user_watches +---------------- + +Every epoll file descriptor can store a number of files to be monitored +for event readiness. Each one of these monitored files constitutes a "watch". +This configuration option sets the maximum number of "watches" that are +allowed for each user. +Each "watch" costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes +on a 64-bit one. +The current default value for ``max_user_watches`` is 4% of the +available low memory, divided by the "watch" cost in bytes. |