The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 9301982c424a003c0095bf157154a85bf5322bd0
Gitweb: https://git.kernel.org/tip/9301982c424a003c0095bf157154a85bf5322bd0
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 18 Jun 2021 16:18:24 +02:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 22 Jun 2021 10:51:23 +02:00
x86/fpu: Preserve supervisor states in sanitize_restored_user_xstate()
sanitize_restored_user_xstate() preserves the supervisor states only
when the fx_only argument is zero, which allows unprivileged user space
to put supervisor states back into init state.
Preserve them unconditionally.
[ bp: Fix a typo or two in the text. ]
Fixes: 5d6b6a6f9b5c ("x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20210618143444.438635017@xxxxxxxxxxxxx
---
arch/x86/kernel/fpu/signal.c | 26 ++++++++------------------
1 file changed, 8 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index ec3ae30..b7b92cd 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -221,28 +221,18 @@ sanitize_restored_user_xstate(union fpregs_state *state,
if (use_xsave()) {
/*
- * Note: we don't need to zero the reserved bits in the
- * xstate_header here because we either didn't copy them at all,
- * or we checked earlier that they aren't set.
+ * Clear all feature bits which are not set in
+ * user_xfeatures and clear all extended features
+ * for fx_only mode.
*/
+ u64 mask = fx_only ? XFEATURE_MASK_FPSSE : user_xfeatures;
/*
- * 'user_xfeatures' might have bits clear which are
- * set in header->xfeatures. This represents features that
- * were in init state prior to a signal delivery, and need
- * to be reset back to the init state. Clear any user
- * feature bits which are set in the kernel buffer to get
- * them back to the init state.
- *
- * Supervisor state is unchanged by input from userspace.
- * Ensure supervisor state bits stay set and supervisor
- * state is not modified.
+ * Supervisor state has to be preserved. The sigframe
+ * restore can only modify user features, i.e. @mask
+ * cannot contain them.
*/
- if (fx_only)
- header->xfeatures = XFEATURE_MASK_FPSSE;
- else
- header->xfeatures &= user_xfeatures |
- xfeatures_mask_supervisor();
+ header->xfeatures &= mask | xfeatures_mask_supervisor();
}
if (use_fxsr()) {
|