summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorAndy Lutomirski <luto@kernel.org>2016-03-16 22:14:22 +0100
committerIngo Molnar <mingo@kernel.org>2016-03-17 09:49:27 +0100
commitc29016cf41fe9fa994a5ecca607cf5f1cd98801e (patch)
treefd6fd91de61bc2e7b407cf13cf2ff07aba334e4a
parentx86/iopl/64: Properly context-switch IOPL on Xen PV (diff)
downloadlinux-c29016cf41fe9fa994a5ecca607cf5f1cd98801e.tar.xz
linux-c29016cf41fe9fa994a5ecca607cf5f1cd98801e.zip
x86/iopl: Fix iopl capability check on Xen PV
iopl(3) is supposed to work if iopl is already 3, even if unprivileged. This didn't work right on Xen PV. Fix it. Reviewewd-by: Jan Beulich <JBeulich@suse.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Beulich <JBeulich@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/8ce12013e6e4c0a44a97e316be4a6faff31bd5ea.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/kernel/ioport.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 37dae792dbbe..589b3193f102 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
SYSCALL_DEFINE1(iopl, unsigned int, level)
{
struct pt_regs *regs = current_pt_regs();
- unsigned int old = (regs->flags >> 12) & 3;
struct thread_struct *t = &current->thread;
+ /*
+ * Careful: the IOPL bits in regs->flags are undefined under Xen PV
+ * and changing them has no effect.
+ */
+ unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+
if (level > 3)
return -EINVAL;
/* Trying to gain more privileges? */
@@ -106,8 +111,9 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
}
- regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
- t->iopl = level << 12;
+ regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
+ (level << X86_EFLAGS_IOPL_BIT);
+ t->iopl = level << X86_EFLAGS_IOPL_BIT;
set_iopl_mask(t->iopl);
return 0;