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Nikolay Aleksandrov fae260fc84 net: bridge: mcast: always update mdb_n_entries for vlan contexts [ Upstream commit `8b769e311a` ] syzbot triggered a warning[1] about the number of mdb entries in a context. It turned out that there are multiple ways to trigger that warning today (some got added during the years), the root cause of the problem is that the increase is done conditionally, and over the years these different conditions increased so there were new ways to trigger the warning, that is to do a decrease which wasn't paired with a previous increase. For example one way to trigger it is with flush: $ ip l add br0 up type bridge vlan_filtering 1 mcast_snooping 1 $ ip l add dumdum up master br0 type dummy $ bridge mdb add dev br0 port dumdum grp 239.0.0.1 permanent vid 1 $ ip link set dev br0 down $ ip link set dev br0 type bridge mcast_vlan_snooping 1 ^^^^ this will enable snooping, but will not update mdb_n_entries because in __br_multicast_enable_port_ctx() we check !netif_running $ bridge mdb flush dev br0 ^^^ this will trigger the warning because it will delete the pg which we added above, which will try to decrease mdb_n_entries Fix the problem by removing the conditional increase and always keep the count up-to-date while the vlan exists. In order to do that we have to first initialize it on port-vlan context creation, and then always increase or decrease the value regardless of mcast options. To keep the current behaviour we have to enforce the mdb limit only if the context is port's or if the port-vlan's mcast snooping is enabled. [1] ------------[ cut here ]------------ n == 0 WARNING: net/bridge/br_multicast.c:718 at br_multicast_port_ngroups_dec_one net/bridge/br_multicast.c:718 [inline], CPU#0: syz.4.4607/22043 WARNING: net/bridge/br_multicast.c:718 at br_multicast_port_ngroups_dec net/bridge/br_multicast.c:771 [inline], CPU#0: syz.4.4607/22043 WARNING: net/bridge/br_multicast.c:718 at br_multicast_del_pg+0x1bbe/0x1e20 net/bridge/br_multicast.c:825, CPU#0: syz.4.4607/22043 Modules linked in: CPU: 0 UID: 0 PID: 22043 Comm: syz.4.4607 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 RIP: 0010:br_multicast_port_ngroups_dec_one net/bridge/br_multicast.c:718 [inline] RIP: 0010:br_multicast_port_ngroups_dec net/bridge/br_multicast.c:771 [inline] RIP: 0010:br_multicast_del_pg+0x1bbe/0x1e20 net/bridge/br_multicast.c:825 Code: 41 5f 5d e9 04 7a 48 f7 e8 3f 73 5c f7 90 0f 0b 90 e9 cf fd ff ff e8 31 73 5c f7 90 0f 0b 90 e9 16 fd ff ff e8 23 73 5c f7 90 <0f> 0b 90 e9 60 fd ff ff e8 15 73 5c f7 eb 05 e8 0e 73 5c f7 48 8b RSP: 0018:ffffc9000c207220 EFLAGS: 00010293 RAX: ffffffff8a68042d RBX: ffff88807c6f1800 RCX: ffff888066e90000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffff888066e90000 R09: 000000000000000c R10: 000000000000000c R11: 0000000000000000 R12: ffff8880303ef800 R13: dffffc0000000000 R14: ffff888050eb11c4 R15: 1ffff1100a1d6238 FS: 00007fa45921b6c0(0000) GS:ffff8881256f5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa4591f9ff8 CR3: 0000000081df2000 CR4: 00000000003526f0 Call Trace: <TASK> br_mdb_flush_pgs net/bridge/br_mdb.c:1525 [inline] br_mdb_flush net/bridge/br_mdb.c:1544 [inline] br_mdb_del_bulk+0x5e2/0xb20 net/bridge/br_mdb.c:1561 rtnl_mdb_del+0x48a/0x640 net/core/rtnetlink.c:-1 rtnetlink_rcv_msg+0x77e/0xbe0 net/core/rtnetlink.c:6967 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa45839aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa45921b028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fa458615fa0 RCX: 00007fa45839aeb9 RDX: 0000000000000000 RSI: 00002000000000c0 RDI: 0000000000000004 RBP: 00007fa458408c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa458616038 R14: 00007fa458615fa0 R15: 00007fff0b59fae8 </TASK> Fixes: `b57e8d870d` ("net: bridge: Maintain number of MDB entries in net_bridge_mcast_port") Reported-by: syzbot+d5d1b7343531d17bd3c5@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/aYrWbRp83MQR1ife@debil/T/#t Reviewed-by: Ido Schimmel <idosch@nvidia.com> Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com> Link: https://patch.msgid.link/20260213070031.1400003-2-nikolay@nvidia.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2026-02-26 14:59:39 -08:00
arch	mips: LOONGSON32: drop a dangling Kconfig symbol	2026-02-26 14:59:35 -08:00
block	block,bfq: fix aux stat accumulation destination	2026-02-11 13:41:47 +01:00
certs	sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3	2024-09-20 19:52:48 +03:00
crypto	crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec	2026-01-30 10:32:12 +01:00
Documentation	dpll: add phase-adjust-gran pin attribute	2026-02-26 14:59:22 -08:00
drivers	xen-netback: reject zero-queue configuration from guest	2026-02-26 14:59:39 -08:00
fs	fs/ntfs3: Fix slab-out-of-bounds read in DeleteIndexEntryRoot	2026-02-26 14:59:36 -08:00
include	net: stmmac: replace has_xxxx with core_type	2026-02-26 14:59:37 -08:00
init	printk changes for 6.18	2025-10-04 11:13:11 -07:00
io_uring	io_uring/cancel: de-unionize file and user_data in struct io_cancel_data	2026-02-26 14:59:36 -08:00
ipc	ipc: don't audit capability check in ipc_permissions()	2026-02-26 14:59:19 -08:00
kernel	bpf: Add a map/btf from a fd array more consistently	2026-02-26 14:59:38 -08:00
lib	objpool: fix the overestimation of object pooling metadata size	2026-02-26 14:59:36 -08:00
LICENSES	LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2	2025-07-24 11:15:39 +02:00
mm	mm/slab: fix false lockdep warning in __kfree_rcu_sheaf()	2026-02-26 14:59:14 -08:00
net	net: bridge: mcast: always update mdb_n_entries for vlan contexts	2026-02-26 14:59:39 -08:00
rust	rust: task: restrict Task::group_leader() to current	2026-02-26 14:59:18 -08:00
samples	samples/ftrace: Adjust LoongArch register restore order in direct calls	2026-01-08 10:17:11 +01:00
scripts	scripts: generate_rust_analyzer: Add compiler_builtins -> core dep	2026-02-06 16:57:42 +01:00
security	evm: Use ordered xattrs list to calculate HMAC in evm_init_hmac()	2026-02-26 14:59:14 -08:00
sound	ASoC: SDCA: Handle volatile controls correctly	2026-02-26 14:59:15 -08:00
tools	libbpf: Fix invalid write loop logic in bpf_linker__add_buf()	2026-02-26 14:59:38 -08:00
usr	gen_init_cpio: Ignore fsync() returning EINVAL on pipes	2025-10-07 09:53:05 -07:00
virt	KVM: Don't clobber irqfd routing type when deassigning irqfd	2026-02-11 13:41:44 +01:00
.clang-format	memblock: drop for_each_free_mem_pfn_range_in_zone_from()	2025-09-14 08:49:03 +03:00
.clippy.toml	rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration	2025-05-07 00:11:47 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.editorconfig	.editorconfig: remove trim_trailing_whitespace option	2024-06-13 16:47:52 +02:00
.get_maintainer.ignore	MAINTAINERS: remove Alyssa Rosenzweig	2025-09-18 21:17:31 +02:00
.gitattributes	.gitattributes: set diff driver for Rust source code files	2023-05-31 17:48:25 +02:00
.gitignore	.gitignore: ignore compile_commands.json globally	2025-08-12 15:53:55 -07:00
.mailmap	8 hotfixes. 4 are cc:stable, 7 are against mm/.	2025-11-26 12:38:05 -08:00
.pylintrc	tools: docs: parse-headers.py: move it from sphinx dir	2025-08-29 15:54:42 -06:00
.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: mark ISDN subsystem as orphan	2025-10-27 17:49:45 -07:00
Kbuild	sched: Make migrate_{en,dis}able() inline	2025-09-25 09:57:16 +02:00
Kconfig	io_uring: Rename KConfig to Kconfig	2025-02-19 14:53:27 -07:00
MAINTAINERS	soc: fixes for 6.18, part 4	2025-11-28 09:57:31 -08:00
Makefile	kbuild: Add objtool to top-level clean target	2026-02-26 14:59:36 -08:00
README	README: Fix spelling	2024-03-18 03:36:32 -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 reStructuredText 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.