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authorAnthony Steinhauser <asteinhauser@google.com>2020-06-07 05:44:19 -0700
committerThomas Gleixner <tglx@linutronix.de>2020-06-09 10:50:55 +0200
commit4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf (patch)
tree0b12815b3168562c696e346601624c8c469a6711 /arch/x86/kernel/cpu/bugs.c
parentdbbe2ad02e9df26e372f38cc3e70dab9222c832e (diff)
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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/cpu/bugs.c')
-rw-r--r--arch/x86/kernel/cpu/bugs.c7
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);