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Steven Rostedt (Google) 1a6edfc7be eventfs: Hold eventfs_mutex when calling callback functions 
commit 44365329f8 upstream.

The callback function that is used to create inodes and dentries is not
protected by anything and the data that is passed to it could become
stale. After eventfs_remove_dir() is called by the tracing system, it is
free to remove the events that are associated to that directory.
Unfortunately, that means the callbacks must not be called after that.

     CPU0				CPU1
     ----				----
 eventfs_root_lookup() {
				 eventfs_remove_dir() {
				      mutex_lock(&event_mutex);
				      ei->is_freed = set;
				      mutex_unlock(&event_mutex);
				 }
				 kfree(event_call);

    for (...) {
      entry = &ei->entries[i];
      r = entry->callback() {
          call = data;		// call == event_call above
          if (call->flags ...)

 [ USE AFTER FREE BUG ]

The safest way to protect this is to wrap the callback with:

 mutex_lock(&eventfs_mutex);
 if (!ei->is_freed)
     r = entry->callback();
 else
     r = -1;
 mutex_unlock(&eventfs_mutex);

This will make sure that the callback will not be called after it is
freed. But now it needs to be known that the callback is called while
holding internal eventfs locks, and that it must not call back into the
eventfs / tracefs system. There's no reason it should anyway, but document
that as well.

Link: https://lore.kernel.org/all/CA+G9fYu9GOEbD=rR5eMR-=HJ8H6rMsbzDC2ZY5=Y50WpWAE7_Q@mail.gmail.com/
Link: https://lkml.kernel.org/r/20231101172649.906696613@goodmis.org

Cc: Ajay Kaher <akaher@vmware.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 5790b1fb3d ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-02-23 09:25:21 +01:00
arch parisc: Fix random data corruption from exception handler 2024-02-23 09:25:18 +01:00
block block: fix partial zone append completion handling in req_bio_endio() 2024-02-23 09:25:18 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: algif_hash - Remove bogus SGL free on zero-length error path 2024-02-23 09:25:11 +01:00
Documentation docs: kernel_feat.py: fix build error for missing files 2024-02-23 09:25:16 +01:00
drivers md: bypass block throttle for superblock update 2024-02-23 09:25:18 +01:00
fs eventfs: Hold eventfs_mutex when calling callback functions 2024-02-23 09:25:21 +01:00
include eventfs: Hold eventfs_mutex when calling callback functions 2024-02-23 09:25:21 +01:00
init update workarounds for gcc "asm goto" issue 2024-02-23 09:24:47 +01:00
io_uring io_uring/net: fix multishot accept overflow handling 2024-02-23 09:25:10 +01:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel eventfs: Use eventfs_remove_events_dir() 2024-02-23 09:25:19 +01:00
lib Revert "kobject: Remove redundant checks for whether ktype is NULL" 2024-02-23 09:24:58 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm blk-wbt: Fix detection of dirty-throttled tasks 2024-02-23 09:25:16 +01:00
net netfilter: ipset: Missing gc cancellations fixed 2024-02-23 09:25:18 +01:00
rust rust: upgrade to Rust 1.73.0 2024-02-16 19:10:43 +01:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:24:47 +01:00
scripts modpost: Add '.ltext' and '.ltext.*' to TEXT_SECTIONS 2024-02-23 09:25:03 +01:00
security lsm: fix the logic in security_inode_getsecctx() 2024-02-23 09:25:02 +01:00
sound ASoC: amd: yc: Add DMI quirk for Lenovo Ideapad Pro 5 16ARP8 2024-02-23 09:25:14 +01:00
tools tools/rtla: Fix Makefile compiler options for clang 2024-02-23 09:25:15 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add Catherine as xfs maintainer for 6.6.y 2024-02-16 19:10:43 +01:00
Makefile Linux 6.6.17 2024-02-16 19:10:57 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.