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| author | Anthony Steinhauser <asteinhauser@google.com> | 2020-06-07 05:44:19 -0700 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-06-09 10:50:55 +0200 |
| commit | 4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf (patch) | |
| tree | 0b12815b3168562c696e346601624c8c469a6711 /arch/x86/kernel | |
| parent | dbbe2ad02e9df26e372f38cc3e70dab9222c832e (diff) | |
| download | linux-4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf.tar.gz linux-4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf.tar.bz2 linux-4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf.zip | |
x86/speculation: PR_SPEC_FORCE_DISABLE enforcement for indirect branches.
Currently, it is possible to enable indirect branch speculation even after
it was force-disabled using the PR_SPEC_FORCE_DISABLE option. Moreover, the
PR_GET_SPECULATION_CTRL command gives afterwards an incorrect result
(force-disabled when it is in fact enabled). This also is inconsistent
vs. STIBP and the documention which cleary states that
PR_SPEC_FORCE_DISABLE cannot be undone.
Fix this by actually enforcing force-disabled indirect branch
speculation. PR_SPEC_ENABLE called after PR_SPEC_FORCE_DISABLE now fails
with -EPERM as described in the documentation.
Fixes: 9137bb27e60e ("x86/speculation: Add prctl() control for indirect branch speculation")
Signed-off-by: Anthony Steinhauser <asteinhauser@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 8d57562b1d2c..56f573aa764f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1175,11 +1175,14 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) return 0; /* * Indirect branch speculation is always disabled in strict - * mode. + * mode. It can neither be enabled if it was force-disabled + * by a previous prctl call. + */ if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT || spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || - spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED) + spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED || + task_spec_ib_force_disable(task)) return -EPERM; task_clear_spec_ib_disable(task); task_update_spec_tif(task); |