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Kuniyuki Iwashima 0d8556922d ipv4: fib: Annotate access to struct fib_alias.fa_state.
[ Upstream commit 6e84fc395e ]

syzbot reported that struct fib_alias.fa_state can be
modified locklessly by RCU readers. [0]

Let's use READ_ONCE()/WRITE_ONCE() properly.

[0]:
BUG: KCSAN: data-race in fib_table_lookup / fib_table_lookup

write to 0xffff88811b06a7fa of 1 bytes by task 4167 on cpu 0:
 fib_alias_accessed net/ipv4/fib_lookup.h:32 [inline]
 fib_table_lookup+0x361/0xd60 net/ipv4/fib_trie.c:1565
 fib_lookup include/net/ip_fib.h:390 [inline]
 ip_route_output_key_hash_rcu+0x378/0x1380 net/ipv4/route.c:2814
 ip_route_output_key_hash net/ipv4/route.c:2705 [inline]
 __ip_route_output_key include/net/route.h:169 [inline]
 ip_route_output_flow+0x65/0x110 net/ipv4/route.c:2932
 udp_sendmsg+0x13c3/0x15d0 net/ipv4/udp.c:1450
 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:859
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x53a/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmmsg+0x185/0x320 net/socket.c:2735
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759
 x64_sys_call+0x1e28/0x3000 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b06a7fa of 1 bytes by task 4168 on cpu 1:
 fib_alias_accessed net/ipv4/fib_lookup.h:31 [inline]
 fib_table_lookup+0x338/0xd60 net/ipv4/fib_trie.c:1565
 fib_lookup include/net/ip_fib.h:390 [inline]
 ip_route_output_key_hash_rcu+0x378/0x1380 net/ipv4/route.c:2814
 ip_route_output_key_hash net/ipv4/route.c:2705 [inline]
 __ip_route_output_key include/net/route.h:169 [inline]
 ip_route_output_flow+0x65/0x110 net/ipv4/route.c:2932
 udp_sendmsg+0x13c3/0x15d0 net/ipv4/udp.c:1450
 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:859
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x53a/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmmsg+0x185/0x320 net/socket.c:2735
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759
 x64_sys_call+0x1e28/0x3000 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4168 Comm: syz.4.206 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025

Reported-by: syzbot+d24f940f770afda885cf@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/69783ead.050a0220.c9109.0013.GAE@google.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260127043528.514160-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:20:10 -05:00
arch openrisc: define arch-specific version of nop() 2026-03-04 07:20:09 -05:00
block blk-mq-debugfs: add missing debugfs_mutex in blk_mq_debugfs_register_hctxs() 2026-03-04 07:19:59 -05:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-02-06 16:41:53 +01:00
Documentation PCI: endpoint: Automatically create a function specific attributes group 2026-02-19 16:21:46 +01:00
drivers wifi: iwlegacy: add missing mutex protection in il3945_store_measurement() 2026-03-04 07:20:10 -05:00
fs ext4: mark group extend fast-commit ineligible 2026-03-04 07:20:08 -05:00
include ipv6: annotate data-races in ip6_multipath_hash_{policy,fields}() 2026-03-04 07:20:08 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring: fix filename leak in __io_openat_prep() 2026-01-19 13:09:54 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel bpf: verifier improvement in 32bit shift sign extension pattern 2026-03-04 07:20:00 -05:00
lib lib/crypto: aes: Fix missing MMU protection for AES S-box 2026-01-19 13:10:13 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/kfence: randomize the freelist on initialization 2026-02-11 13:35:27 +01:00
net ipv4: fib: Annotate access to struct fib_alias.fa_state. 2026-03-04 07:20:10 -05:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts modpost: Amend ppc64 save/restfpr symnames for -Os build 2026-03-04 07:20:06 -05:00
security apparmor: fix invalid deref of rawdata when export_binary is unset 2026-03-04 07:19:53 -05:00
sound ALSA: usb-audio: Add iface reset and delay quirk for AB13X USB Audio 2026-03-04 07:20:07 -05:00
tools tools/power cpupower: Reset errno before strtoull() 2026-03-04 07:19:57 -05:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:35:27 +01:00
.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 5.15.201 2026-02-19 16:21:47 +01:00
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.