[PATCH 5.12 079/110] x86/fpu: Preserve supervisor states in sanitize_restored_user_xstate()
From: Sasha Levin <sashal@kernel.org>
Date: 2021-06-28 14:25:09
Also in:
lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Thomas Gleixner <redacted>
commit 9301982c424a003c0095bf157154a85bf5322bd0 upstream.
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 <redacted>
Signed-off-by: Borislav Petkov <redacted>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210618143444.438635017@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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 ec3ae3054792..b7b92cdf3add 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()) {
--
2.30.2