Commit a6323757 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

x86/ldt/64: Refresh DS and ES when modify_ldt changes an entry

On x86_32, modify_ldt() implicitly refreshes the cached DS and ES
segments because they are refreshed on return to usermode.

On x86_64, they're not refreshed on return to usermode.  To improve
determinism and match x86_32's behavior, refresh them when we update
the LDT.

This avoids a situation in which the DS points to a descriptor that is
changed but the old cached segment persists until the next reschedule.
If this happens, then the user-visible state will change
nondeterministically some time after modify_ldt() returns, which is
unfortunate.
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Chang Seok <chang.seok.bae@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 81d38719
...@@ -21,6 +21,25 @@ ...@@ -21,6 +21,25 @@
#include <asm/mmu_context.h> #include <asm/mmu_context.h>
#include <asm/syscalls.h> #include <asm/syscalls.h>
static void refresh_ldt_segments(void)
{
#ifdef CONFIG_X86_64
unsigned short sel;
/*
* Make sure that the cached DS and ES descriptors match the updated
* LDT.
*/
savesegment(ds, sel);
if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT)
loadsegment(ds, sel);
savesegment(es, sel);
if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT)
loadsegment(es, sel);
#endif
}
/* context.lock is held for us, so we don't need any locking. */ /* context.lock is held for us, so we don't need any locking. */
static void flush_ldt(void *__mm) static void flush_ldt(void *__mm)
{ {
...@@ -32,6 +51,8 @@ static void flush_ldt(void *__mm) ...@@ -32,6 +51,8 @@ static void flush_ldt(void *__mm)
pc = &mm->context; pc = &mm->context;
set_ldt(pc->ldt->entries, pc->ldt->nr_entries); set_ldt(pc->ldt->entries, pc->ldt->nr_entries);
refresh_ldt_segments();
} }
/* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */ /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
......
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