{"id":"DEBIAN-CVE-2024-35871","details":"In the Linux kernel, the following vulnerability has been resolved:  riscv: process: Fix kernel gp leakage  childregs represents the registers which are active for the new thread in user context. For a kernel thread, childregs-\u003egp is never used since the kernel gp is not touched by switch_to. For a user mode helper, the gp value can be observed in user space after execve or possibly by other means.  [From the email thread]  The /* Kernel thread */ comment is somewhat inaccurate in that it is also used for user_mode_helper threads, which exec a user process, e.g. /sbin/init or when /proc/sys/kernel/core_pattern is a pipe. Such threads do not have PF_KTHREAD set and are valid targets for ptrace etc. even before they exec.  childregs is the *user* context during syscall execution and it is observable from userspace in at least five ways:  1. kernel_execve does not currently clear integer registers, so the starting    register state for PID 1 and other user processes started by the kernel has    sp = user stack, gp = kernel __global_pointer$, all other integer registers    zeroed by the memset in the patch comment.     This is a bug in its own right, but I'm unwilling to bet that it is the only    way to exploit the issue addressed by this patch.  2. ptrace(PTRACE_GETREGSET): you can PTRACE_ATTACH to a user_mode_helper thread    before it execs, but ptrace requires SIGSTOP to be delivered which can only    happen at user/kernel boundaries.  3. /proc/*/task/*/syscall: this is perfectly happy to read pt_regs for    user_mode_helpers before the exec completes, but gp is not one of the    registers it returns.  4. PERF_SAMPLE_REGS_USER: LOCKDOWN_PERF normally prevents access to kernel    addresses via PERF_SAMPLE_REGS_INTR, but due to this bug kernel addresses    are also exposed via PERF_SAMPLE_REGS_USER which is permitted under    LOCKDOWN_PERF. I have not attempted to write exploit code.  5. Much of the tracing infrastructure allows access to user registers. I have    not attempted to determine which forms of tracing allow access to user    registers without already allowing access to kernel registers.","modified":"2026-09-01T20:05:25.994663978Z","published":"2024-05-19T09:15:08.507Z","upstream":["CVE-2024-35871"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-35871"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.85-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35871.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.8.9-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35871.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.8.9-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35871.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"}]}