{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-74363", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-74363" ], "published": "2026-08-15T06:04:33Z", "summary": "bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fix UAF by restoring RCU-delayed inode freeing in bpffs\n\ncommit 4f375ade6aa9 (\"bpf: Avoid RCU context warning when unpinning\nhtab with internal structs\") moved inode cleanup from ->free_inode()\ninto ->destroy_inode() to avoid sleeping in RCU context when calling\nbpf_any_put(). However this removed the RCU delay on freeing the\ninode itself and the cached symlink body (i_link), both of which\ncan be accessed by RCU pathwalk (pick_link, may_lookup etc.).\n\nThis causes a use-after-free when a concurrent unlinkat() drops the\nlast inode reference and destroy_inode() frees the inode immediately,\nwhile another task is still walking the path in RCU mode and reads\ninode->i_opflags (offset +2) inside current_time() -> is_mgtime().\n\nKASAN reports:\n BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313\n Read of size 2 at addr ffff8880407e4282 (offset +2 = i_opflags)\n\nThe rules (per Al Viro):\n ->destroy_inode() called immediately, can sleep, use for blocking\n cleanup e.g. bpf_any_put()\n ->free_inode() called after RCU grace period, use for freeing\n inode and anything RCU-accessible e.g. i_link\n\nFix: split the two concerns properly:\n - keep bpf_any_put() in bpf_destroy_inode() since it is blocking\n and needs to run promptly\n - introduce bpf_free_inode() to handle kfree(i_link) and\n free_inode_nonrcu() with proper RCU delay, preventing the UAF", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.62-1+rpt1~bookworm", "1:6.12.75-1+rpt1~bookworm", "1:6.12.87-1+rpt1~bookworm", "1:6.12.93-1+rpt1", "1:6.12.96-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.62+rpt-rpi-2712", "binary_version": "1:6.12.62-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.62+rpt-rpi-v6", "binary_version": "1:6.12.62-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.62+rpt-rpi-v7", "binary_version": "1:6.12.62-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.62+rpt-rpi-v7l", "binary_version": "1:6.12.62-1+rpt1~bookworm" }, { "binary_name": "linux-image-6.12.62+rpt-rpi-v8", "binary_version": "1:6.12.62-1+rpt1~bookworm" }, { "binary_name": 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"FIX", "url": "https://git.kernel.org/stable/c/c70d0f9114c3cc156f6029a400c4eb7e6f7c82b2" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/53649846e0437d1d9b7cb993cfe54c367addf7ae" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/61f19729728243c82476dee31315143ed3275e7f" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0497ff765746d9b2d17445c8f7cc737b36c0152a" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b93c55b4932dd7e32dca8cf34a3443cc87a02906" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-17T05:50:24Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The bug is triggered through local VFS and bpf(2) syscalls on bpffs (unlinkat/symlinkat/openat/stat and BPF_OBJ_GET/BPF_OBJ_PIN) racing RCU pathwalk; BPF/bpffs is not reachable from remote network services.\nAC:L - Exploitation requires a race between unlinkat dropping the last bpffs inode reference and concurrent RCU pathwalk, but the attacker controls both sides with parallel threads/syscalls and syzbot reliably reproduces the UAF without external timing.\nPR:L - Any local user with write access to a bpffs mount (default sticky world-writable /sys/fs/bpf) can create symlinks or pin/unpin BPF objects without init-namespace root, including via unprivileged BPF or delegated bpffs mounts in user namespaces.\nUI:N - No victim action is required; the attacker programmatically races their own unlink/pathwalk operations on bpffs objects they can create and remove.\nS:U - This is a kernel heap use-after-free in bpffs inode lifetime management, enabling local privilege escalation within the same security domain rather than crossing VM, IOMMU, or sandbox boundaries.\nC:H - KASAN confirmed slab use-after-free reading freed inode->i_opflags during RCU pathwalk; UAF of struct inode enables subsequent arbitrary kernel memory disclosure via heap reuse.\nI:H - Premature inode freeing permits attacker-controlled heap reuse and spraying, providing a standard kernel UAF path to arbitrary write and potential code execution beyond the initial 2-byte read.\nA:H - Concurrent RCU pathwalk of a prematurely freed bpffs inode triggers KASAN slab-UAF and kernel oops; repeated triggering can panic the system or cause denial of service." } } }