{"id":"CVE-2024-35892","state":"PUBLISHED","title":"net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fix lockdep splat in qdisc_tree_reduce_backlog()\n\nqdisc_tree_reduce_backlog() is called with the qdisc lock held,\nnot RTNL.\n\nWe must use qdisc_lookup_rcu() instead of qdisc_lookup()\n\nsyzbot reported:\n\nWARNING: suspicious RCU usage\n6.1.74-syzkaller #0 Not tainted\n-----------------------------\nnet/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage!\n\nother info that might help us debug this:\n\nrcu_scheduler_active = 2, debug_locks = 1\n3 locks held by udevd/1142:\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282\n  #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]\n  #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792\n\nstack backtrace:\nCPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024\nCall Trace:\n <TASK>\n  [<ffffffff85b85f14>] __dump_stack lib/dump_stack.c:88 [inline]\n  [<ffffffff85b85f14>] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106\n  [<ffffffff85b86007>] dump_stack+0x15/0x1e lib/dump_stack.c:113\n  [<ffffffff81802299>] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592\n  [<ffffffff84f0054c>] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305\n  [<ffffffff84f037c3>] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811\n  [<ffffffff84f5b78c>] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51\n  [<ffffffff84fbcf63>] qdisc_enqueue include/net/sch_generic.h:833 [inline]\n  [<ffffffff84fbcf63>] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723\n  [<ffffffff84eecab9>] dequeue_skb net/sched/sch_generic.c:292 [inline]\n  [<ffffffff84eecab9>] qdisc_restart net/sched/sch_generic.c:397 [inline]\n  [<ffffffff84eecab9>] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415\n  [<ffffffff84d7aa96>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125\n  [<ffffffff84d85d29>] net_tx_action+0x7c9/0x970 net/core/dev.c:5313\n  [<ffffffff85e002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616\n  [<ffffffff81568bca>] invoke_softirq kernel/softirq.c:447 [inline]\n  [<ffffffff81568bca>] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700\n  [<ffffffff81568ae9>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712\n  [<ffffffff85b89f52>] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107\n  [<ffffffff85c00ccb>] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656","publishedAt":"2024-05-19T08:34:47.914Z","updatedAt":"2026-05-23T15:44:48.543Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9d9a38b5639fcefacc1e977567fb4b4e4a74d0b3","status":"affected","lessThan":"b7d1ce2cc7192e8a037faa3f5d3ba72c25976460","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"c040b99461a5bfc14c2d0cbb1780fcc3a4706c7e","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"07696415526bee0607e495017369c7303a4792e1","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"7eb322360b0266481e560d1807ee79e0cef5742b","versionType":"git"},{"version":"3a4741bb13caf482b877b10ac1bcf7390cad7077","status":"affected","versionType":"git"},{"version":"6.1.34","status":"affected","lessThan":"6.1.85","versionType":"semver"},{"version":"6.3.8","status":"affected","lessThan":"6.4","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.1.85","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.26","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.8.5","status":"unaffected","lessThanOrEqual":"6.8.*","versionType":"semver"},{"version":"6.9","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"]}],"references":["https://git.kernel.org/stable/c/b7d1ce2cc7192e8a037faa3f5d3ba72c25976460","https://git.kernel.org/stable/c/c040b99461a5bfc14c2d0cbb1780fcc3a4706c7e","https://git.kernel.org/stable/c/07696415526bee0607e495017369c7303a4792e1","https://git.kernel.org/stable/c/7eb322360b0266481e560d1807ee79e0cef5742b"],"weaknesses":[],"ingestedAt":"2026-10-29T20:07:30.303Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2024/35xxx/CVE-2024-35892.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2024-35892","state":"PUBLISHED","datePublished":"2024-05-19T08:34:47.914Z","dateUpdated":"2026-05-23T15:44:48.543Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-05-17T13:50:33.113Z"},"containers":{"cna":{"title":"net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fix lockdep splat in qdisc_tree_reduce_backlog()\n\nqdisc_tree_reduce_backlog() is called with the qdisc lock held,\nnot RTNL.\n\nWe must use qdisc_lookup_rcu() instead of qdisc_lookup()\n\nsyzbot reported:\n\nWARNING: suspicious RCU usage\n6.1.74-syzkaller #0 Not tainted\n-----------------------------\nnet/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage!\n\nother info that might help us debug this:\n\nrcu_scheduler_active = 2, debug_locks = 1\n3 locks held by udevd/1142:\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]\n  #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282\n  #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]\n  #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]\n  #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792\n\nstack backtrace:\nCPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024\nCall Trace:\n <TASK>\n  [<ffffffff85b85f14>] __dump_stack lib/dump_stack.c:88 [inline]\n  [<ffffffff85b85f14>] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106\n  [<ffffffff85b86007>] dump_stack+0x15/0x1e lib/dump_stack.c:113\n  [<ffffffff81802299>] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592\n  [<ffffffff84f0054c>] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305\n  [<ffffffff84f037c3>] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811\n  [<ffffffff84f5b78c>] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51\n  [<ffffffff84fbcf63>] qdisc_enqueue include/net/sch_generic.h:833 [inline]\n  [<ffffffff84fbcf63>] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723\n  [<ffffffff84eecab9>] dequeue_skb net/sched/sch_generic.c:292 [inline]\n  [<ffffffff84eecab9>] qdisc_restart net/sched/sch_generic.c:397 [inline]\n  [<ffffffff84eecab9>] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415\n  [<ffffffff84d7aa96>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125\n  [<ffffffff84d85d29>] net_tx_action+0x7c9/0x970 net/core/dev.c:5313\n  [<ffffffff85e002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616\n  [<ffffffff81568bca>] invoke_softirq kernel/softirq.c:447 [inline]\n  [<ffffffff81568bca>] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700\n  [<ffffffff81568ae9>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712\n  [<ffffffff85b89f52>] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107\n  [<ffffffff85c00ccb>] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9d9a38b5639fcefacc1e977567fb4b4e4a74d0b3","status":"affected","lessThan":"b7d1ce2cc7192e8a037faa3f5d3ba72c25976460","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"c040b99461a5bfc14c2d0cbb1780fcc3a4706c7e","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"07696415526bee0607e495017369c7303a4792e1","versionType":"git"},{"version":"d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb","status":"affected","lessThan":"7eb322360b0266481e560d1807ee79e0cef5742b","versionType":"git"},{"version":"3a4741bb13caf482b877b10ac1bcf7390cad7077","status":"affected","versionType":"git"},{"version":"6.1.34","status":"affected","lessThan":"6.1.85","versionType":"semver"},{"version":"6.3.8","status":"affected","lessThan":"6.4","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.1.85","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.26","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.8.5","status":"unaffected","lessThanOrEqual":"6.8.*","versionType":"semver"},{"version":"6.9","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/b7d1ce2cc7192e8a037faa3f5d3ba72c25976460"},{"url":"https://git.kernel.org/stable/c/c040b99461a5bfc14c2d0cbb1780fcc3a4706c7e"},{"url":"https://git.kernel.org/stable/c/07696415526bee0607e495017369c7303a4792e1"},{"url":"https://git.kernel.org/stable/c/7eb322360b0266481e560d1807ee79e0cef5742b"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-23T15:44:48.543Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.34","versionEndExcluding":"6.1.85"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.6.26"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.8.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA 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