diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-03-09 19:00:33 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-03-10 09:48:14 +0100 |
| commit | 2a41aa4feb25af3ead60b740c43df80c576efea2 (patch) | |
| tree | f982f3b4787e2e31cce97673ce733f9a4b0f1574 /arch | |
| parent | 7536656f08d0c1a3b4c487d00785c5186ec6f533 (diff) | |
| download | linux-0-day-2a41aa4feb25af3ead60b740c43df80c576efea2.tar.gz linux-0-day-2a41aa4feb25af3ead60b740c43df80c576efea2.tar.xz | |
x86/entry/32: Add and check a stack canary for the SYSENTER stack
The first instruction of the SYSENTER entry runs on its own tiny
stack. That stack can be used if a #DB or NMI is delivered before
the SYSENTER prologue switches to a real stack.
We have code in place to prevent us from overflowing the tiny stack.
For added paranoia, add a canary to the stack and check it in
do_debug() -- that way, if something goes wrong with the #DB logic,
we'll eventually notice.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/6ff9a806f39098b166dc2c41c1db744df5272f29.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/traps.c | 8 |
3 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 7cd01b71b5bdc..50a6dc871cc08 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -299,8 +299,9 @@ struct tss_struct { #ifdef CONFIG_X86_32 /* - * Space for the temporary SYSENTER stack: + * Space for the temporary SYSENTER stack. */ + unsigned long SYSENTER_stack_canary; unsigned long SYSENTER_stack[64]; #endif diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9f7c21c22477e..ee9a9792caeb3 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -57,6 +57,9 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = { */ .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, #endif +#ifdef CONFIG_X86_32 + .SYSENTER_stack_canary = STACK_END_MAGIC, +#endif }; EXPORT_PER_CPU_SYMBOL(cpu_tss); diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index b0ddb81926f92..49e2e775f507a 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -713,6 +713,14 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) debug_stack_usage_dec(); exit: +#if defined(CONFIG_X86_32) + /* + * This is the most likely code path that involves non-trivial use + * of the SYSENTER stack. Check that we haven't overrun it. + */ + WARN(this_cpu_read(cpu_tss.SYSENTER_stack_canary) != STACK_END_MAGIC, + "Overran or corrupted SYSENTER stack\n"); +#endif ist_exit(regs); } NOKPROBE_SYMBOL(do_debug); |