linux-kernel - [tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_user_to

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Date:   Tue, 26 Sep 2017 01:37:29 -0700
From:   tip-bot for Eric Biggers <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, haokexin@...il.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, riel@...hat.com,
        keescook@...omium.org, ebiggers3@...il.com, mhalcrow@...gle.com,
        fenghua.yu@...el.com, luto@...capital.net, yu-cheng.yu@...el.com,
        luto@...nel.org, ebiggers@...gle.com, tglx@...utronix.de,
        oleg@...hat.com, dvyukov@...gle.com, hpa@...or.com,
        dave.hansen@...ux.intel.com, wanpeng.li@...mail.com, bp@...en8.de,
        torvalds@...ux-foundation.org, akpm@...ux-foundation.org
Subject: [tip:x86/fpu] x86/fpu: Use validate_xstate_header() to validate the
 xstate_header in copy_user_to_xstate()

Commit-ID:  98c0fad9d60e8b2cd47e15b7bee7df343648f5bb
Gitweb:     http://git.kernel.org/tip/98c0fad9d60e8b2cd47e15b7bee7df343648f5bb
Author:     Eric Biggers <ebiggers@...gle.com>
AuthorDate: Sun, 24 Sep 2017 12:59:12 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 26 Sep 2017 09:43:48 +0200

x86/fpu: Use validate_xstate_header() to validate the xstate_header in copy_user_to_xstate()

Tighten the checks in copy_user_to_xstate().

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Eric Biggers <ebiggers3@...il.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kevin Hao <haokexin@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael Halcrow <mhalcrow@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc: kernel-hardening@...ts.openwall.com
Link: http://lkml.kernel.org/r/20170924105913.9157-10-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/xstate.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index b6d78b7..f1d5476 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1188,16 +1188,15 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
 }
 
 /*
- * Convert from a ptrace standard-format user-space buffer to kernel XSAVES format
- * and copy to the target thread. This is called from xstateregs_set() and
- * there we check the CPU has XSAVES and a whole standard-sized buffer
- * exists.
+ * Convert from a ptrace or sigreturn standard-format user-space buffer to
+ * kernel XSAVES format and copy to the target thread. This is called from
+ * xstateregs_set(), as well as potentially from the sigreturn() and
+ * rt_sigreturn() system calls.
  */
 int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 {
 	unsigned int offset, size;
 	int i;
-	u64 allowed_features;
 	struct xstate_header hdr;
 
 	offset = offsetof(struct xregs_state, header);
@@ -1206,12 +1205,7 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 	if (__copy_from_user(&hdr, ubuf + offset, size))
 		return -EFAULT;
 
-	/*
-	 * Reject if the user sets any disabled or supervisor features:
-	 */
-	allowed_features = xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR;
-
-	if (hdr.xfeatures & ~allowed_features)
+	if (validate_xstate_header(&hdr))
 		return -EINVAL;
 
 	for (i = 0; i < XFEATURE_MAX; i++) {