From: Josh Poimboeuf jpoimboe@redhat.com
stable inclusion from stable-v5.10.105 commit d04937ae94903087279e4a016b7741cdee59d521 category: bugfix bugzilla: 186453 https://gitee.com/src-openeuler/kernel/issues/I50WBM CVE: CVE-2022-0001
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 0de05d056afdb00eca8c7bbb0c79a3438daf700c upstream.
The commit
44a3918c8245 ("x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting")
added a warning for the "eIBRS + unprivileged eBPF" combination, which has been shown to be vulnerable against Spectre v2 BHB-based attacks.
However, there's no warning about the "eIBRS + LFENCE retpoline + unprivileged eBPF" combo. The LFENCE adds more protection by shortening the speculation window after a mispredicted branch. That makes an attack significantly more difficult, even with unprivileged eBPF. So at least for now the logic doesn't warn about that combination.
But if you then add SMT into the mix, the SMT attack angle weakens the effectiveness of the LFENCE considerably.
So extend the "eIBRS + unprivileged eBPF" warning to also include the "eIBRS + LFENCE + unprivileged eBPF + SMT" case.
[ bp: Massage commit message. ]
Suggested-by: Alyssa Milburn alyssa.milburn@linux.intel.com Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Signed-off-by: Borislav Petkov bp@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jiahao chenjiahao16@huawei.com Reviewed-by: Liao Chang liaochang1@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- arch/x86/kernel/cpu/bugs.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index bade6afeb169..78b9514a3844 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -616,12 +616,27 @@ static inline const char *spectre_v2_module_string(void) { return ""; }
#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n" #define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n" +#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
#ifdef CONFIG_BPF_SYSCALL void unpriv_ebpf_notify(int new_state) { - if (spectre_v2_enabled == SPECTRE_V2_EIBRS && !new_state) + if (new_state) + return; + + /* Unprivileged eBPF is enabled */ + + switch (spectre_v2_enabled) { + case SPECTRE_V2_EIBRS: pr_err(SPECTRE_V2_EIBRS_EBPF_MSG); + break; + case SPECTRE_V2_EIBRS_LFENCE: + if (sched_smt_active()) + pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); + break; + default: + break; + } } #endif
@@ -1081,6 +1096,10 @@ void cpu_bugs_smt_update(void) { mutex_lock(&spec_ctrl_mutex);
+ if (sched_smt_active() && unprivileged_ebpf_enabled() && + spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) + pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG); + switch (spectre_v2_user_stibp) { case SPECTRE_V2_USER_NONE: break; @@ -1723,7 +1742,11 @@ static ssize_t spectre_v2_show_state(char *buf) return sprintf(buf, "Vulnerable: LFENCE\n");
if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled()) - return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n"); + return sprintf(buf, "Vulnerable: eIBRS with unprivileged eBPF\n"); + + if (sched_smt_active() && unprivileged_ebpf_enabled() && + spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE) + return sprintf(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n");
return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],