From: "tip-bot for H. Peter Anvin" <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org,
tglx@linutronix.de, hpa@linux.intel.com
Subject: [tip:x86/espfix] x86-32, espfix: Remove filter for espfix32 due to race
Date: Wed, 30 Apr 2014 14:19:10 -0700 [thread overview]
Message-ID: <tip-246f2d2ee1d715e1077fc47d61c394569c8ee692@git.kernel.org> (raw)
In-Reply-To: <1398816946-3351-1-git-send-email-hpa@linux.intel.com>
Commit-ID: 246f2d2ee1d715e1077fc47d61c394569c8ee692
Gitweb: http://git.kernel.org/tip/246f2d2ee1d715e1077fc47d61c394569c8ee692
Author: H. Peter Anvin <hpa@linux.intel.com>
AuthorDate: Wed, 30 Apr 2014 14:03:25 -0700
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Wed, 30 Apr 2014 14:14:49 -0700
x86-32, espfix: Remove filter for espfix32 due to race
It is not safe to use LAR to filter when to go down the espfix path,
because the LDT is per-process (rather than per-thread) and another
thread might change the descriptors behind our back. Fortunately it
is always *safe* (if a bit slow) to go down the espfix path, and a
32-bit LDT stack segment is extremely rare.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com
Cc: <stable@vger.kernel.org> # consider after upstream merge
---
arch/x86/kernel/entry_32.S | 5 -----
1 file changed, 5 deletions(-)
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index a2a4f46..2780b8f 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -551,11 +551,6 @@ ENTRY(iret_exc)
CFI_RESTORE_STATE
ldt_ss:
- larl PT_OLDSS(%esp), %eax
- jnz restore_nocheck
- testl $0x00400000, %eax # returning to 32bit stack?
- jnz restore_nocheck # allright, normal return
-
#ifdef CONFIG_PARAVIRT
/*
* The kernel can't run on a non-flat stack if paravirt mode
next prev parent reply other threads:[~2014-04-30 21:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-30 0:15 [PATCH] x86-64, espfix: Don't leak bits 31:16 of %esp returning to 16-bit stack H. Peter Anvin
2014-04-30 0:57 ` Linus Torvalds
2014-04-30 10:38 ` Borislav Petkov
2014-04-30 16:18 ` H. Peter Anvin
2014-04-30 16:33 ` H. Peter Anvin
2014-04-30 17:16 ` Borislav Petkov
2014-04-30 17:25 ` H. Peter Anvin
2014-04-30 21:18 ` [tip:x86/espfix] x86-64, espfix: Don't leak bits 31: 16 " tip-bot for H. Peter Anvin
2014-04-30 21:19 ` tip-bot for H. Peter Anvin [this message]
2014-05-04 17:07 ` [tip:x86/espfix] x86, espfix: Make espfix64 a Kconfig option, fix UML tip-bot for H. Peter Anvin
2014-05-04 19:03 ` [tip:x86/espfix] x86, espfix: Make it possible do disable 16-bit support tip-bot for H. Peter Anvin
2014-05-04 19:30 ` [tip:x86/espfix] x86, espfix: Make it possible to " tip-bot for H. Peter Anvin
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