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x86/bugs: Add a separate config for RETBLEED

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Currently, the CONFIG_SPECULATION_MITIGATIONS is halfway populated,
where some mitigations have entries in Kconfig, and they could be
modified, while others mitigations do not have Kconfig entries, and
could not be controlled at build time.

Create an entry for the RETBLEED CPU mitigation under
CONFIG_SPECULATION_MITIGATIONS. This allow users to enable or disable
it at compilation time.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240729164105.554296-6-leitao@debian.org
This commit is contained in:
Breno Leitao 2024-07-29 09:40:53 -07:00 committed by Borislav Petkov (AMD)
parent 3a4ee4ff81
commit 894e28857c
2 changed files with 14 additions and 1 deletions
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13
arch/x86/Kconfig
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@ -2692,6 +2692,19 @@ config MITIGATION_L1TF
hardware vulnerability which allows unprivileged speculative access to data
available in the Level 1 Data Cache.
See <file:Documentation/admin-guide/hw-vuln/l1tf.rst
config MITIGATION_RETBLEED
bool "Mitigate RETBleed hardware bug"
depends on (CPU_SUP_INTEL && MITIGATION_SPECTRE_V2) || MITIGATION_UNRET_ENTRY || MITIGATION_IBPB_ENTRY
default y
help
Enable mitigation for RETBleed (Arbitrary Speculative Code Execution
with Return Instructions) vulnerability. RETBleed is a speculative
execution attack which takes advantage of microarchitectural behavior
in many modern microprocessors, similar to Spectre v2. An
unprivileged attacker can use these flaws to bypass conventional
memory security restrictions to gain read access to privileged memory
that would otherwise be inaccessible.
endif
config ARCH_HAS_ADD_PAGES

2
arch/x86/kernel/cpu/bugs.c
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@ -989,7 +989,7 @@ static const char * const retbleed_strings[] = {
static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
RETBLEED_MITIGATION_NONE;
static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init =
RETBLEED_CMD_AUTO;
IS_ENABLED(CONFIG_MITIGATION_RETBLEED) ? RETBLEED_CMD_AUTO : RETBLEED_CMD_OFF;
static int __ro_after_init retbleed_nosmt = false;