Commit c29016cf authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

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.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b7a58459
...@@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) ...@@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
SYSCALL_DEFINE1(iopl, unsigned int, level) SYSCALL_DEFINE1(iopl, unsigned int, level)
{ {
struct pt_regs *regs = current_pt_regs(); struct pt_regs *regs = current_pt_regs();
unsigned int old = (regs->flags >> 12) & 3;
struct thread_struct *t = &current->thread; 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) if (level > 3)
return -EINVAL; return -EINVAL;
/* Trying to gain more privileges? */ /* Trying to gain more privileges? */
...@@ -106,8 +111,9 @@ SYSCALL_DEFINE1(iopl, unsigned int, level) ...@@ -106,8 +111,9 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
if (!capable(CAP_SYS_RAWIO)) if (!capable(CAP_SYS_RAWIO))
return -EPERM; return -EPERM;
} }
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
t->iopl = level << 12; (level << X86_EFLAGS_IOPL_BIT);
t->iopl = level << X86_EFLAGS_IOPL_BIT;
set_iopl_mask(t->iopl); set_iopl_mask(t->iopl);
return 0; return 0;
......
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