kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-22 19:14:51 +00:00
Code Issues Releases Packages Activity
No description
1,159,922 commits 117 branches 5,803 tags 5.7 GiB
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Krister Johansen 12771050b6 dm thin: make get_first_thin use rcu-safe list first function 
commit 80f130bfad upstream.

The documentation in rculist.h explains the absence of list_empty_rcu()
and cautions programmers against relying on a list_empty() ->
list_first() sequence in RCU safe code.  This is because each of these
functions performs its own READ_ONCE() of the list head.  This can lead
to a situation where the list_empty() sees a valid list entry, but the
subsequent list_first() sees a different view of list head state after a
modification.

In the case of dm-thin, this author had a production box crash from a GP
fault in the process_deferred_bios path.  This function saw a valid list
head in get_first_thin() but when it subsequently dereferenced that and
turned it into a thin_c, it got the inside of the struct pool, since the
list was now empty and referring to itself.  The kernel on which this
occurred printed both a warning about a refcount_t being saturated, and
a UBSAN error for an out-of-bounds cpuid access in the queued spinlock,
prior to the fault itself.  When the resulting kdump was examined, it
was possible to see another thread patiently waiting in thin_dtr's
synchronize_rcu.

The thin_dtr call managed to pull the thin_c out of the active thins
list (and have it be the last entry in the active_thins list) at just
the wrong moment which lead to this crash.

Fortunately, the fix here is straight forward.  Switch get_first_thin()
function to use list_first_or_null_rcu() which performs just a single
READ_ONCE() and returns NULL if the list is already empty.

This was run against the devicemapper test suite's thin-provisioning
suites for delete and suspend and no regressions were observed.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Fixes: b10ebd34cc ("dm thin: fix rcu_read_lock being held in code that can sleep")
Cc: stable@vger.kernel.org
Acked-by: Ming-Hung Tsai <mtsai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-01-17 13:34:41 +01:00
arch ARC: build: Try to guess GCC variant of cross compiler 2025-01-09 13:30:05 +01:00
block blk-mq: register cpuhp callback after hctx is added to xarray table 2025-01-02 10:30:52 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: api - Add crypto_clone_tfm 2024-12-14 19:53:51 +01:00
Documentation dt-bindings: display: adi,adv7533: Drop single lane support 2025-01-09 13:30:06 +01:00
drivers dm thin: make get_first_thin use rcu-safe list first function 2025-01-17 13:34:41 +01:00
fs ksmbd: fix unexpectedly changed path in ksmbd_vfs_kern_path_locked 2025-01-17 13:34:41 +01:00
include tcp/dccp: allow a connection when sk_max_ack_backlog is zero 2025-01-17 13:34:38 +01:00
init initramfs: avoid filename buffer overrun 2024-12-14 19:53:14 +01:00
io_uring io_uring/sqpoll: fix sqpoll error handling races 2025-01-02 10:30:54 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-14 19:54:06 +01:00
kernel kcov: mark in_softirq_really() as __always_inline 2025-01-09 13:30:05 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 19:54:37 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm: vmscan: account for free pages to prevent infinite Loop in throttle_direct_reclaim() 2025-01-09 13:30:07 +01:00
net sched: sch_cake: add bounds checks to host bulk flow fairness counts 2025-01-17 13:34:40 +01:00
rust rust: macros: provide correct provenance when constructing THIS_MODULE 2024-10-17 15:22:24 +02:00
samples samples/bpf: Fix a resource leak 2024-12-14 19:54:40 +01:00
scripts scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity 2025-01-17 13:34:38 +01:00
security selinux: ignore unknown extended permissions 2025-01-09 13:29:56 +01:00
sound ASoC: mediatek: disable buffer pre-allocation 2025-01-17 13:34:38 +01:00
tools stddef: make __struct_group() UAPI C++-friendly 2025-01-02 10:30:51 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:46:21 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -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 15:21:15 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.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 MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 leah to 6.1 MAINTAINERS file 2024-05-17 11:56:16 +02:00
Makefile Linux 6.1.124 2025-01-09 13:30:07 +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.