[PATCH] x86: General protection fault after STR (32 bit systems only)

Srinivas Pandruvada
2015-06-11T23:48:09Z

Suspend to RAM process is returning to userspsace with DS set to KERNEL_DS
after resume, this cause general protection fault. This is very difficult
to reproduce, but this does happen on 32 bit systems. This crash is not
reproduced after save/restore DS during calls to _save_processor_state/
__restore_processor_state respectively.
Similar issue was reported in the past
https://bugzilla.kernel.org/show_bug.cgi?id=61781, for which the root cause
was not identified.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/include/asm/suspend_32.h | 2 +-
arch/x86/power/cpu.c | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/suspend_32.h b/arch/x86/include/asm/suspend_32.h
index 552d6c9..3503d0b 100644
--- a/arch/x86/include/asm/suspend_32.h
+++ b/arch/x86/include/asm/suspend_32.h
@@ -11,7 +11,7 @@

/* image of the saved processor state */
struct saved_context {
- u16 es, fs, gs, ss;
+ u16 ds, es, fs, gs, ss;
unsigned long cr0, cr2, cr3, cr4;
u64 misc_enable;
bool misc_enable_saved;
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 757678f..e0dfb01 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -79,6 +79,7 @@ static void __save_processor_state(struct saved_context *ctxt)
* segment registers
*/
#ifdef CONFIG_X86_32
+ savesegment(ds, ctxt->ds);
savesegment(es, ctxt->es);
savesegment(fs, ctxt->fs);
savesegment(gs, ctxt->gs);
@@ -198,6 +199,7 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
* segment registers
*/
#ifdef CONFIG_X86_32
+ loadsegment(ds, ctxt->ds);
loadsegment(es, ctxt->es);
loadsegment(fs, ctxt->fs);
loadsegment(gs, ctxt->gs);
--
1.9.3