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Commit c29016cf authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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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: default avatarJan Beulich <JBeulich@suse.com>
Signed-off-by: default avatarAndy 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: default avatarIngo Molnar <mingo@kernel.org>
parent b7a58459

arch/x86/kernel/ioport.c

+9 −3
Original line number Diff line number Diff line
@@ -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;