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Amir Goldstein 2e8d4e8cb8 fsnotify: opt-in for permission events at file open time
[ Upstream commit a94204f4d4 ]

Legacy inotify/fanotify listeners can add watches for events on inode,
parent or mount and expect to get events (e.g. FS_MODIFY) on files that
were already open at the time of setting up the watches.

fanotify permission events are typically used by Anti-malware sofware,
that is watching the entire mount and it is not common to have more that
one Anti-malware engine installed on a system.

To reduce the overhead of the fsnotify_file_perm() hooks on every file
access, relax the semantics of the legacy FAN_ACCESS_PERM event to generate
events only if there were *any* permission event listeners on the
filesystem at the time that the file was opened.

The new semantic is implemented by extending the FMODE_NONOTIFY bit into
two FMODE_NONOTIFY_* bits, that are used to store a mode for which of the
events types to report.

This is going to apply to the new fanotify pre-content events in order
to reduce the cost of the new pre-content event vfs hooks.

[Thanks to Bert Karwatzki <spasswolf@web.de> for reporting a bug in this
code with CONFIG_FANOTIFY_ACCESS_PERMISSIONS disabled]

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wj8L=mtcRTi=NECHMGfZQgXOp_uix1YVh04fEmrKaMnXA@mail.gmail.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/5ea5f8e283d1edb55aa79c35187bfe344056af14.1731684329.git.josef@toxicpanda.com
Stable-dep-of: db1856ea91 ("binfmt_misc: restore write access when removing an entry")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-08-23 14:17:29 +02:00
arch fs/resctrl: Fix double-add of pseudo-locked region's RMID to free list 2026-08-23 14:17:24 +02:00
block partitions: aix: bound the pp_count scan to the ppe array 2026-07-24 15:51:24 +02:00
certs X.509: Fix validation of ASN.1 certificate header 2026-07-24 15:51:59 +02:00
crypto crypto: rsa-pkcs1pad: Don't WARN on an empty digest 2026-08-19 17:13:55 +02:00
Documentation PCI: Move Resizable BAR code to rebar.c 2026-07-24 15:51:58 +02:00
drivers ice: fix memory leak in ice_lbtest_prepare_rings() 2026-08-23 14:17:29 +02:00
fs ksmbd: reject repeated SMB2 NEGOTIATE requests 2026-08-23 14:17:28 +02:00
include fsnotify: opt-in for permission events at file open time 2026-08-23 14:17:29 +02:00
init bootconfig: move xbc_snprint_cmdline() to lib/bootconfig.c 2026-08-23 14:17:24 +02:00
io_uring io_uring/io-wq: re-check IO_WQ_BIT_EXIT for each linked work item 2026-07-24 15:51:21 +02:00
ipc ipc/shm: serialize orphan cleanup with shm_nattch updates 2026-06-19 13:33:38 +02:00
kernel ftrace: Add global mutex to serialize trace_parser access 2026-08-23 14:17:28 +02:00
lib bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline() 2026-08-23 14:17:24 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/vmstat: fold stranded per-cpu node stats when a node comes online 2026-08-23 14:17:28 +02:00
net net: pktgen: fix proc entry use-after-free 2026-08-23 14:17:29 +02:00
samples tracing/events: Fix to check the simple_tsk_fn creation 2026-07-24 15:51:42 +02:00
scripts kconfig: fix potential NULL pointer dereference in conf_askvalue 2026-07-24 15:51:28 +02:00
security selinux: avoid sk_socket dereference in selinux_sctp_bind_connect() 2026-08-23 14:17:21 +02:00
sound ALSA: seq: close a re-opened queue timer in the destructor 2026-08-23 14:17:26 +02:00
tools selftests/ftrace: refactor eprobes test to fix argument checks 2026-08-19 17:14:13 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Move kvm_io_bus_get_dev() locking responsibilities to callers 2026-07-24 15:52:02 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.216 2026-08-19 17:14:18 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.