kernel/linux.git/net/ipv4/igmp.c, branch v7.1.6

ipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer()

2026-07-24T14:20:45+00:00

[ Upstream commit 3546deaa0c30a14c7cdb5dc8f2432cb428f0cd36 ] When a timer is deleted and not re-armed in igmp_mod_timer(), or stopped in igmp_stop_timer(), the code currently decrements the reference counter of the multicast list entry @im using refcount_dec(&im->refcnt). However, both functions can be called from the RCU reader path: - igmp_mod_timer() via igmp_heard_query() -> for_each_pmc_rcu() - igmp_stop_timer() via igmp_rcv() -> igmp_heard_report() If the group im was concurrently removed from the list by ip_mc_dec_group(), its reference count might have already been decremented to 1. In this case, timer_delete() succeeds, and refcount_dec() decrements the refcount from 1 to 0. Since refcount_dec() does not free the object when it hits 0 (unlike ip_ma_put()), the im structure is leaked. Fix this by using ip_ma_put(im) instead of refcount_dec(&im->refcnt), and deferring the put until after the spinlock is released. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260705181756.963063-4-edumazet@google.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

ipv4: igmp: annotate data-races around timer-related fields

2026-07-24T14:20:45+00:00

[ Upstream commit 3289d17b7a1321e103b8aec4ad82675c03c4764f ] /proc/net/igmp walks the multicast list locklessly under RCU and reads timer-related fields (im->tm_running, im->reporter, im->timer.expires) to print the timer state of multicast memberships. Concurrently, these fields are modified under im->lock spinlock in timer management paths (igmp_stop_timer(), igmp_start_timer(), and igmp_timer_expire()). Fix this intentional lockless snapshot by annotating the lockless reads with READ_ONCE() and the updates with WRITE_ONCE(). Signed-off-by: Yuyang Huang Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260605014318.3890804-3-yuyanghuang@google.com Signed-off-by: Paolo Abeni Stable-dep-of: 3546deaa0c30 ("ipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer()") Signed-off-by: Sasha Levin

ipv4: igmp: annotate data-races around im->users

2026-07-24T14:20:45+00:00

[ Upstream commit 061c0aa740d5d3847cd600a74c66a165bee1fbe0 ] /proc/net/igmp walks IPv4 multicast memberships under RCU and prints im->users without holding RTNL, while multicast join and leave paths update the field while holding RTNL. Annotate this intentional lockless snapshot with READ_ONCE() and the matching writers with WRITE_ONCE(). Signed-off-by: Yuyang Huang Reviewed-by: Jiayuan Chen Reviewed-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260522093906.39764-1-sigefriedhyy@gmail.com Signed-off-by: Jakub Kicinski Stable-dep-of: 3546deaa0c30 ("ipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer()") Signed-off-by: Sasha Levin

ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()

2026-07-24T14:20:45+00:00

[ Upstream commit 7b19c0f81ed1fdaec6bc522569be367199a9edf3 ] A race condition exists between device teardown (inetdev_destroy) and incoming IGMP query processing (igmp_rcv), leading to a Use-After-Free in the IGMP timer callback. During device destruction, inetdev_destroy() drops the primary reference to in_device, which can drop its refcount to 0. The actual freeing of in_device memory is deferred via RCU (using call_rcu()). Concurrently, igmp_rcv() runs under RCU read lock and obtains the in_device pointer. Because the memory is RCU-protected, CPU-0 can safely dereference in_device even if its refcount has hit 0. However, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it attempts to acquire a reference using in_dev_hold(). This increments the refcount from 0 to 1, triggering a "refcount_t: addition on 0" warning. Since the in_device memory is still scheduled to be freed after the RCU grace period (as the free callback does not check the refcount again), the device is freed while the timer is still armed. When the timer expires, it accesses the freed memory, causing a kernel panic. Fix this by using refcount_inc_not_zero() (via a new helper in_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not arm the timer. A similar issue in IPv6 MLD is fixed in a subsequent patch. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Zero Day Initiative Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260705181756.963063-2-edumazet@google.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

ipv4: igmp: remove multicast group from hash table on device destruction

2026-07-18T14:55:27+00:00

commit 7993211bde166471dffac074dc965489f86531f8 upstream. When a device is destroyed under RTNL, ip_mc_destroy_dev() iterates through the multicast list and calls ip_ma_put() on each membership, scheduling them for RCU reclamation. However, they are not unlinked from the device's multicast hash table (mc_hash). Since the device remains published in dev->ip_ptr until after ip_mc_destroy_dev() completes, concurrent RCU readers traversing mc_hash can still locate and access the multicast group after its refcount is decremented. If the RCU callback runs and frees the group while a reader is accessing it, a use-after-free occurs. Fix this by unlinking the multicast group from mc_hash using ip_mc_hash_remove() before scheduling it for reclamation. BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x149/0x3f0 Read of size 4 at addr ffff888009bf1408 by task mausezahn/2276 Call Trace: dump_stack_lvl+0x67/0x90 print_report+0x175/0x7c0 kasan_report+0x147/0x180 ip_check_mc_rcu+0x149/0x3f0 udp_v4_early_demux+0x36d/0x12d0 ip_rcv_finish_core+0xb8b/0x1390 ip_rcv_finish+0x54/0x120 NF_HOOK+0x213/0x2b0 __netif_receive_skb+0x126/0x340 process_backlog+0x4f2/0xf00 __napi_poll+0x92/0x2c0 net_rx_action+0x583/0xc60 handle_softirqs+0x236/0x7f0 do_softirq+0x57/0x80 Allocated by task 2239: kasan_save_track+0x3e/0x80 __kasan_kmalloc+0x72/0x90 ____ip_mc_inc_group+0x31a/0xa40 __ip_mc_join_group+0x334/0x3f0 do_ip_setsockopt+0x16fa/0x2010 ip_setsockopt+0x3f/0x90 do_sock_setsockopt+0x1ad/0x300 Freed by task 0: kasan_save_track+0x3e/0x80 kasan_save_free_info+0x40/0x50 __kasan_slab_free+0x3a/0x60 __rcu_free_sheaf_prepare+0xd4/0x220 rcu_free_sheaf+0x36/0x190 rcu_core+0x8d9/0x12f0 handle_softirqs+0x236/0x7f0 Fixes: e9897071350b ("igmp: hash a hash table to speedup ip_check_mc_rcu()") Cc: stable@vger.kernel.org Signed-off-by: Yuyang Huang Reviewed-by: Kuniyuki Iwashima Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260701235014.73505-1-yuyanghuang@google.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

ipv4: igmp: annotate data-races in igmp_heard_query()

2026-05-02T00:11:42+00:00

Multiple cpus can run igmp_heard_query() concurrently. Add missing READ_ONCE()/WRITE_ONCE() over following in_dev fields. - mr_qrv - mr_qi - mr_qri - mr_v1_seen - mr_v2_seen Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+ae9a171f239b14485310@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/69f38675.050a0220.3cbe47.0002.GAE@google.com Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260430164836.872079-1-edumazet@google.com Signed-off-by: Jakub Kicinski

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

ipv4: igmp: annotate data-races around idev->mr_maxdelay

2026-01-25T22:45:14+00:00

idev->mr_maxdelay is read and written locklessly, add READ_ONCE()/WRITE_ONCE() annotations. While we are at it, make this field an u32. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://patch.msgid.link/20260122172247.2429403-1-edumazet@google.com Signed-off-by: Jakub Kicinski

ipv4: adopt dst_dev, skb_dst_dev and skb_dst_dev_net[_rcu]

2025-07-02T21:32:30+00:00

Use the new helpers as a first step to deal with potential dst->dev races. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250630121934.3399505-8-edumazet@google.com Signed-off-by: Jakub Kicinski

treewide, timers: Rename from_timer() to timer_container_of()

2025-06-08T07:07:37+00:00

Move this API to the canonical timer_*() namespace. [ tglx: Redone against pre rc1 ] Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com