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| author | Kim Phillips <kim.phillips@amd.com> | 2022-08-08 09:32:33 -0500 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2022-08-08 19:12:17 +0200 |
| commit | e6cfcdda8cbe81eaf821c897369a65fec987b404 (patch) | |
| tree | 8e6b4e846ddbf6f7d0919a3a210042df92984865 /arch | |
| parent | de979c83574abf6e78f3fa65b716515c91b2613d (diff) | |
| download | linux-stable-e6cfcdda8cbe81eaf821c897369a65fec987b404.tar.gz linux-stable-e6cfcdda8cbe81eaf821c897369a65fec987b404.tar.bz2 linux-stable-e6cfcdda8cbe81eaf821c897369a65fec987b404.zip | |
x86/bugs: Enable STIBP for IBPB mitigated RETBleed
AMD's "Technical Guidance for Mitigating Branch Type Confusion,
Rev. 1.0 2022-07-12" whitepaper, under section 6.1.2 "IBPB On
Privileged Mode Entry / SMT Safety" says:
Similar to the Jmp2Ret mitigation, if the code on the sibling thread
cannot be trusted, software should set STIBP to 1 or disable SMT to
ensure SMT safety when using this mitigation.
So, like already being done for retbleed=unret, and now also for
retbleed=ibpb, force STIBP on machines that have it, and report its SMT
vulnerability status accordingly.
[ bp: Remove the "we" and remove "[AMD]" applicability parameter which
doesn't work here. ]
Fixes: 3ebc17006888 ("x86/bugs: Add retbleed=ibpb")
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org # 5.10, 5.15, 5.19
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Link: https://lore.kernel.org/r/20220804192201.439596-1-kim.phillips@amd.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6761668100b9..d50686ca5870 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -152,7 +152,7 @@ void __init check_bugs(void) /* * spectre_v2_user_select_mitigation() relies on the state set by * retbleed_select_mitigation(); specifically the STIBP selection is - * forced for UNRET. + * forced for UNRET or IBPB. */ spectre_v2_user_select_mitigation(); ssb_select_mitigation(); @@ -1179,7 +1179,8 @@ spectre_v2_user_select_mitigation(void) boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) mode = SPECTRE_V2_USER_STRICT_PREFERRED; - if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { + if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET || + retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { if (mode != SPECTRE_V2_USER_STRICT && mode != SPECTRE_V2_USER_STRICT_PREFERRED) pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n"); @@ -2320,10 +2321,11 @@ static ssize_t srbds_show_state(char *buf) static ssize_t retbleed_show_state(char *buf) { - if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { + if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET || + retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) - return sprintf(buf, "Vulnerable: untrained return thunk on non-Zen uarch\n"); + return sprintf(buf, "Vulnerable: untrained return thunk / IBPB on non-AMD based uarch\n"); return sprintf(buf, "%s; SMT %s\n", retbleed_strings[retbleed_mitigation], |