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Message-Id: <20141206174148.982073196@1wt.eu>
Date: Sat, 06 Dec 2014 18:42:01 +0100
From: Willy Tarreau <w@....eu>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Andy Lutomirski <luto@...capital.net>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Willy Tarreau <w@....eu>
Subject: [ 13/25] x86_64, traps: Stop using IST for #SS
2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski <luto@...capital.net>
On a 32-bit kernel, this has no effect, since there are no IST stacks.
On a 64-bit kernel, #SS can only happen in user code, on a failed iret
to user space, a canonical violation on access via RSP or RBP, or a
genuine stack segment violation in 32-bit kernel code. The first two
cases don't need IST, and the latter two cases are unlikely fatal bugs,
and promoting them to double faults would be fine.
This fixes a bug in which the espfix64 code mishandles a stack segment
violation.
This saves 4k of memory per CPU and a tiny bit of code.
Signed-off-by: Andy Lutomirski <luto@...capital.net>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
(cherry picked from commit 6f442be2fb22be02cafa606f1769fa1e6f894441)
[wt: no CONFIG_TRACING on 2.6.32, Fixes CVE-2014-9090]
Signed-off-by: Willy Tarreau <w@....eu>
---
arch/x86/include/asm/page_32_types.h | 1 -
arch/x86/include/asm/page_64_types.h | 11 +++++------
arch/x86/kernel/dumpstack_64.c | 1 -
arch/x86/kernel/entry_64.S | 2 +-
arch/x86/kernel/traps.c | 14 +-------------
5 files changed, 7 insertions(+), 22 deletions(-)
diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h
index 6f1b733..775c92f 100644
--- a/arch/x86/include/asm/page_32_types.h
+++ b/arch/x86/include/asm/page_32_types.h
@@ -22,7 +22,6 @@
#endif
#define THREAD_SIZE (PAGE_SIZE << THREAD_ORDER)
-#define STACKFAULT_STACK 0
#define DOUBLEFAULT_STACK 1
#define NMI_STACK 0
#define DEBUG_STACK 0
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 7639dbf..a9e9937 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -14,12 +14,11 @@
#define IRQ_STACK_ORDER 2
#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)
-#define STACKFAULT_STACK 1
-#define DOUBLEFAULT_STACK 2
-#define NMI_STACK 3
-#define DEBUG_STACK 4
-#define MCE_STACK 5
-#define N_EXCEPTION_STACKS 5 /* hw limit: 7 */
+#define DOUBLEFAULT_STACK 1
+#define NMI_STACK 2
+#define DEBUG_STACK 3
+#define MCE_STACK 4
+#define N_EXCEPTION_STACKS 4 /* hw limit: 7 */
#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT)
#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1))
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index a071e6b..5dc0882 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -23,7 +23,6 @@ static char x86_stack_ids[][8] = {
[DEBUG_STACK - 1] = "#DB",
[NMI_STACK - 1] = "NMI",
[DOUBLEFAULT_STACK - 1] = "#DF",
- [STACKFAULT_STACK - 1] = "#SS",
[MCE_STACK - 1] = "#MC",
#if DEBUG_STKSZ > EXCEPTION_STKSZ
[N_EXCEPTION_STACKS ...
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 4313d48..8e2f14a 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1434,7 +1434,7 @@ END(xen_failsafe_callback)
paranoidzeroentry_ist debug do_debug DEBUG_STACK
paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
-paranoiderrorentry stack_segment do_stack_segment
+errorentry stack_segment do_stack_segment
#ifdef CONFIG_XEN
zeroentry xen_debug do_debug
zeroentry xen_int3 do_int3
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7e37dce..c4cc05a 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -220,23 +220,11 @@ DO_ERROR_INFO(6, SIGILL, "invalid opcode", invalid_op, ILL_ILLOPN, regs->ip)
DO_ERROR(9, SIGFPE, "coprocessor segment overrun", coprocessor_segment_overrun)
DO_ERROR(10, SIGSEGV, "invalid TSS", invalid_TSS)
DO_ERROR(11, SIGBUS, "segment not present", segment_not_present)
-#ifdef CONFIG_X86_32
DO_ERROR(12, SIGBUS, "stack segment", stack_segment)
-#endif
DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)
#ifdef CONFIG_X86_64
/* Runs on IST stack */
-dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
-{
- if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
- 12, SIGBUS) == NOTIFY_STOP)
- return;
- preempt_conditional_sti(regs);
- do_trap(12, SIGBUS, "stack segment", regs, error_code, NULL);
- preempt_conditional_cli(regs);
-}
-
dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
{
static const char str[] = "double fault";
@@ -927,7 +915,7 @@ void __init trap_init(void)
set_intr_gate(9, &coprocessor_segment_overrun);
set_intr_gate(10, &invalid_TSS);
set_intr_gate(11, &segment_not_present);
- set_intr_gate_ist(12, &stack_segment, STACKFAULT_STACK);
+ set_intr_gate(12, &stack_segment);
set_intr_gate(13, &general_protection);
set_intr_gate(14, &page_fault);
set_intr_gate(15, &spurious_interrupt_bug);
--
1.7.12.2.21.g234cd45.dirty
--
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