diff options
| author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2018-07-09 16:35:34 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-07-25 11:23:58 +0200 |
| commit | 6ac85d22332118d2dc449536110a31a5ca3956b0 (patch) | |
| tree | 9148bab9992a116fb6edd7e803ce5fa26cae3e64 /arch/x86/kernel | |
| parent | 76267a8a19cdc40094796a2bd032eaf437774c35 (diff) | |
x86/apm: Don't access __preempt_count with zeroed fs
commit 6f6060a5c9cc76fdbc22748264e6aa3779ec2427 upstream.
APM_DO_POP_SEGS does not restore fs/gs which were zeroed by
APM_DO_ZERO_SEGS. Trying to access __preempt_count with
zeroed fs doesn't really work.
Move the ibrs call outside the APM_DO_SAVE_SEGS/APM_DO_RESTORE_SEGS
invocations so that fs is actually restored before calling
preempt_enable().
Fixes the following sort of oopses:
[ 0.313581] general protection fault: 0000 [#1] PREEMPT SMP
[ 0.313803] Modules linked in:
[ 0.314040] CPU: 0 PID: 268 Comm: kapmd Not tainted 4.16.0-rc1-triton-bisect-00090-gdd84441a7971 #19
[ 0.316161] EIP: __apm_bios_call_simple+0xc8/0x170
[ 0.316161] EFLAGS: 00210016 CPU: 0
[ 0.316161] EAX: 00000102 EBX: 00000000 ECX: 00000102 EDX: 00000000
[ 0.316161] ESI: 0000530e EDI: dea95f64 EBP: dea95f18 ESP: dea95ef0
[ 0.316161] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
[ 0.316161] CR0: 80050033 CR2: 00000000 CR3: 015d3000 CR4: 000006d0
[ 0.316161] Call Trace:
[ 0.316161] ? cpumask_weight.constprop.15+0x20/0x20
[ 0.316161] on_cpu0+0x44/0x70
[ 0.316161] apm+0x54e/0x720
[ 0.316161] ? __switch_to_asm+0x26/0x40
[ 0.316161] ? __schedule+0x17d/0x590
[ 0.316161] kthread+0xc0/0xf0
[ 0.316161] ? proc_apm_show+0x150/0x150
[ 0.316161] ? kthread_create_worker_on_cpu+0x20/0x20
[ 0.316161] ret_from_fork+0x2e/0x38
[ 0.316161] Code: da 8e c2 8e e2 8e ea 57 55 2e ff 1d e0 bb 5d b1 0f 92 c3 5d 5f 07 1f 89 47 0c 90 8d b4 26 00 00 00 00 90 8d b4 26 00 00 00 00 90 <64> ff 0d 84 16 5c b1 74 7f 8b 45 dc 8e e0 8b 45 d8 8e e8 8b 45
[ 0.316161] EIP: __apm_bios_call_simple+0xc8/0x170 SS:ESP: 0068:dea95ef0
[ 0.316161] ---[ end trace 656253db2deaa12c ]---
Fixes: dd84441a7971 ("x86/speculation: Use IBRS if available before calling into firmware")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180709133534.5963-1-ville.syrjala@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/apm_32.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c index 51287cd90bf6..313a85a7b222 100644 --- a/arch/x86/kernel/apm_32.c +++ b/arch/x86/kernel/apm_32.c @@ -239,6 +239,7 @@ #include <asm/olpc.h> #include <asm/paravirt.h> #include <asm/reboot.h> +#include <asm/nospec-branch.h> #if defined(CONFIG_APM_DISPLAY_BLANK) && defined(CONFIG_VT) extern int (*console_blank_hook)(int); @@ -613,11 +614,13 @@ static long __apm_bios_call(void *_call) gdt[0x40 / 8] = bad_bios_desc; apm_irq_save(flags); + firmware_restrict_branch_speculation_start(); APM_DO_SAVE_SEGS; apm_bios_call_asm(call->func, call->ebx, call->ecx, &call->eax, &call->ebx, &call->ecx, &call->edx, &call->esi); APM_DO_RESTORE_SEGS; + firmware_restrict_branch_speculation_end(); apm_irq_restore(flags); gdt[0x40 / 8] = save_desc_40; put_cpu(); @@ -689,10 +692,12 @@ static long __apm_bios_call_simple(void *_call) gdt[0x40 / 8] = bad_bios_desc; apm_irq_save(flags); + firmware_restrict_branch_speculation_start(); APM_DO_SAVE_SEGS; error = apm_bios_call_simple_asm(call->func, call->ebx, call->ecx, &call->eax); APM_DO_RESTORE_SEGS; + firmware_restrict_branch_speculation_end(); apm_irq_restore(flags); gdt[0x40 / 8] = save_desc_40; put_cpu(); |