{"id":"CVE-2024-35860","state":"PUBLISHED","title":"bpf: support deferring bpf_link dealloc to after RCU grace period","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: support deferring bpf_link dealloc to after RCU grace period\n\nBPF link for some program types is passed as a \"context\" which can be\nused by those BPF programs to look up additional information. E.g., for\nmulti-kprobes and multi-uprobes, link is used to fetch BPF cookie values.\n\nBecause of this runtime dependency, when bpf_link refcnt drops to zero\nthere could still be active BPF programs running accessing link data.\n\nThis patch adds generic support to defer bpf_link dealloc callback to\nafter RCU GP, if requested. This is done by exposing two different\ndeallocation callbacks, one synchronous and one deferred. If deferred\none is provided, bpf_link_free() will schedule dealloc_deferred()\ncallback to happen after RCU GP.\n\nBPF is using two flavors of RCU: \"classic\" non-sleepable one and RCU\ntasks trace one. The latter is used when sleepable BPF programs are\nused. bpf_link_free() accommodates that by checking underlying BPF\nprogram's sleepable flag, and goes either through normal RCU GP only for\nnon-sleepable, or through RCU tasks trace GP *and* then normal RCU GP\n(taking into account rcu_trace_implies_rcu_gp() optimization), if BPF\nprogram is sleepable.\n\nWe use this for multi-kprobe and multi-uprobe links, which dereference\nlink during program run. We also preventively switch raw_tp link to use\ndeferred dealloc callback, as upcoming changes in bpf-next tree expose\nraw_tp link data (specifically, cookie value) to BPF program at runtime\nas well.","publishedAt":"2024-05-19T08:34:19.368Z","updatedAt":"2026-10-30T12:18:16.969Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"ac48dc6ac9240f73bf08d29edf65c2deca93ee5d","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"876941f533e7b47fc69977fc4551c02f2d18af97","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"5d8d447777564b35f67000e7838e7ccb64d525c8","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/bpf.h","kernel/bpf/syscall.c","kernel/trace/bpf_trace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.191","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":["include/linux/bpf.h","kernel/bpf/syscall.c","kernel/trace/bpf_trace.c"]}],"references":["https://git.kernel.org/stable/c/ac48dc6ac9240f73bf08d29edf65c2deca93ee5d","https://git.kernel.org/stable/c/876941f533e7b47fc69977fc4551c02f2d18af97","https://git.kernel.org/stable/c/5d8d447777564b35f67000e7838e7ccb64d525c8","https://git.kernel.org/stable/c/1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce"],"weaknesses":[],"ingestedAt":"2026-10-30T12:34:06.950Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2024/35xxx/CVE-2024-35860.json","commit":"db8103c5921aac81d5d90efcf3745980dafabf49","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2024-35860","state":"PUBLISHED","datePublished":"2024-05-19T08:34:19.368Z","dateUpdated":"2026-10-30T12:18:16.969Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-05-17T13:50:33.107Z"},"containers":{"cna":{"title":"bpf: support deferring bpf_link dealloc to after RCU grace period","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: support deferring bpf_link dealloc to after RCU grace period\n\nBPF link for some program types is passed as a \"context\" which can be\nused by those BPF programs to look up additional information. E.g., for\nmulti-kprobes and multi-uprobes, link is used to fetch BPF cookie values.\n\nBecause of this runtime dependency, when bpf_link refcnt drops to zero\nthere could still be active BPF programs running accessing link data.\n\nThis patch adds generic support to defer bpf_link dealloc callback to\nafter RCU GP, if requested. This is done by exposing two different\ndeallocation callbacks, one synchronous and one deferred. If deferred\none is provided, bpf_link_free() will schedule dealloc_deferred()\ncallback to happen after RCU GP.\n\nBPF is using two flavors of RCU: \"classic\" non-sleepable one and RCU\ntasks trace one. The latter is used when sleepable BPF programs are\nused. bpf_link_free() accommodates that by checking underlying BPF\nprogram's sleepable flag, and goes either through normal RCU GP only for\nnon-sleepable, or through RCU tasks trace GP *and* then normal RCU GP\n(taking into account rcu_trace_implies_rcu_gp() optimization), if BPF\nprogram is sleepable.\n\nWe use this for multi-kprobe and multi-uprobe links, which dereference\nlink during program run. We also preventively switch raw_tp link to use\ndeferred dealloc callback, as upcoming changes in bpf-next tree expose\nraw_tp link data (specifically, cookie value) to BPF program at runtime\nas well."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"ac48dc6ac9240f73bf08d29edf65c2deca93ee5d","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"876941f533e7b47fc69977fc4551c02f2d18af97","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"5d8d447777564b35f67000e7838e7ccb64d525c8","versionType":"git"},{"version":"0dcac272540613d41c05e89679e4ddb978b612f1","status":"affected","lessThan":"1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/bpf.h","kernel/bpf/syscall.c","kernel/trace/bpf_trace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.191","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":["include/linux/bpf.h","kernel/bpf/syscall.c","kernel/trace/bpf_trace.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ac48dc6ac9240f73bf08d29edf65c2deca93ee5d"},{"url":"https://git.kernel.org/stable/c/876941f533e7b47fc69977fc4551c02f2d18af97"},{"url":"https://git.kernel.org/stable/c/5d8d447777564b35f67000e7838e7ccb64d525c8"},{"url":"https://git.kernel.org/stable/c/1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerability is reached solely through the local `bpf()` syscall — `BPF_PROG_LOAD` plus `BPF_LINK_CREATE` for a kprobe_multi/uprobe_multi link, then closing the link fd while the probes fire. No network or remote-peer input is involved anywhere on the path.\nAC:L - The attacker controls both sides of the race: it picks which kernel/user functions are probed (including ones that block, so return-hooks fire arbitrarily late), drives them in a loop across all CPUs, and closes the link fd at will; three independent syzbot reproducers hit it in practice, so no condition outside attacker influence is required.\nPR:L - Creating these links needs CAP_BPF+CAP_PERFMON, which `bpf_token_capable()` grants at `ns_capable()` level to a delegated BPF token inside a container, and which ordinary non-root tracing/observability service accounts routinely hold — that is a low-privileged account, not administrative control of the host.\nUI:N - The whole sequence — load program, create link, trigger the probes, close the fd — happens inside the attacker's own process. No action by any other user or administrator is needed.\nS:U - The use-after-free and everything it corrupts stay inside the kernel's own memory and privilege domain; no hypervisor, IOMMU, or other security-authority boundary is crossed.\nC:H - `bpf_kprobe_multi_cookie()` bsearches the freed `addrs` array and returns `*cookie` from the freed `cookies` allocation directly to the running BPF program, which can exfiltrate it via a map — a read primitive over attacker-sprayed reclaimed slab, and the freed link is fully groomable.\nI:H - `kprobe_multi_link_prog_run()`/`uprobe_prog_run()` load `link->link.prog` out of freed memory and then indirect-call through it via `bpf_prog_run()`, and `fprobe_exit_handler()` calls `fp->exit_handler` from the same freed object — an attacker-controlled function-pointer dispatch giving control-flow hijack and full kernel-integrity compromise.\nA:H - Even without weaponization, dereferencing and calling through the freed link produces a KASAN slab-use-after-free splat and a wild indirect branch — an immediate oops or panic — and the attacker can repeat the create/trigger/close cycle indefinitely."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:18:16.969Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.6.26"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.8.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.9"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/876941f533e7b47fc69977fc4551c02f2d18af97","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/5d8d447777564b35f67000e7838e7ccb64d525c8","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/1a80dbcb2dbaf6e4c216e62e30fa7d3daa8001ce","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-02T03:21:48.532Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2024-35860","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-09-10T15:41:33.868687Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-09-11T17:33:17.617Z"}}]}}}