{"id":"CVE-2024-35871","summary":"riscv: process: Fix kernel gp leakage","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: process: Fix kernel gp leakage\n\nchildregs represents the registers which are active for the new thread\nin user context. For a kernel thread, childregs-\u003egp is never used since\nthe kernel gp is not touched by switch_to. For a user mode helper, the\ngp value can be observed in user space after execve or possibly by other\nmeans.\n\n[From the email thread]\n\nThe /* Kernel thread */ comment is somewhat inaccurate in that it is also used\nfor user_mode_helper threads, which exec a user process, e.g. /sbin/init or\nwhen /proc/sys/kernel/core_pattern is a pipe. Such threads do not have\nPF_KTHREAD set and are valid targets for ptrace etc. even before they exec.\n\nchildregs is the *user* context during syscall execution and it is observable\nfrom userspace in at least five ways:\n\n1. kernel_execve does not currently clear integer registers, so the starting\n   register state for PID 1 and other user processes started by the kernel has\n   sp = user stack, gp = kernel __global_pointer$, all other integer registers\n   zeroed by the memset in the patch comment.\n\n   This is a bug in its own right, but I'm unwilling to bet that it is the only\n   way to exploit the issue addressed by this patch.\n\n2. ptrace(PTRACE_GETREGSET): you can PTRACE_ATTACH to a user_mode_helper thread\n   before it execs, but ptrace requires SIGSTOP to be delivered which can only\n   happen at user/kernel boundaries.\n\n3. /proc/*/task/*/syscall: this is perfectly happy to read pt_regs for\n   user_mode_helpers before the exec completes, but gp is not one of the\n   registers it returns.\n\n4. PERF_SAMPLE_REGS_USER: LOCKDOWN_PERF normally prevents access to kernel\n   addresses via PERF_SAMPLE_REGS_INTR, but due to this bug kernel addresses\n   are also exposed via PERF_SAMPLE_REGS_USER which is permitted under\n   LOCKDOWN_PERF. I have not attempted to write exploit code.\n\n5. Much of the tracing infrastructure allows access to user registers. I have\n   not attempted to determine which forms of tracing allow access to user\n   registers without already allowing access to kernel registers.","modified":"2026-03-20T12:36:42.242232Z","published":"2024-05-19T08:34:29.292Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/35xxx/CVE-2024-35871.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/00effef72c98294edb1efa87ffa0f6cfb61b36a4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9abc3e6f1116adb7a2d4fbb8ce20c37916976bf5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d14fa1fcf69db9d070e75f1c4425211fa619dfc8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d8dcba0691b8e42bddb61aab201e4d918a08e5d9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dff6072124f6df77bfd36951fbd88565746980ef"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f6583444d7e78dae750798552b65a2519ff3ca84"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/35xxx/CVE-2024-35871.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-35871"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7db91e57a0acde126a162ababfb1e0ab190130cb"},{"fixed":"9abc3e6f1116adb7a2d4fbb8ce20c37916976bf5"},{"fixed":"dff6072124f6df77bfd36951fbd88565746980ef"},{"fixed":"f6583444d7e78dae750798552b65a2519ff3ca84"},{"fixed":"00effef72c98294edb1efa87ffa0f6cfb61b36a4"},{"fixed":"d8dcba0691b8e42bddb61aab201e4d918a08e5d9"},{"fixed":"d14fa1fcf69db9d070e75f1c4425211fa619dfc8"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-35871.json"}}],"schema_version":"1.7.5"}