3.2.80-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <[email protected]> commit c29016cf41fe9fa994a5ecca607cf5f1cd98801e upstream. 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 <[email protected]> Signed-off-by: Andy Lutomirski <[email protected]> Cc: Andrew Cooper <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Boris Ostrovsky <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: David Vrabel <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/8ce12013e6e4c0a44a97e316be4a6faff31bd5ea.1458162709.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/kernel/ioport.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -95,9 +95,14 @@ asmlinkage long sys_ioperm(unsigned long */ long sys_iopl(unsigned int level, struct pt_regs *regs) { - unsigned int old = (regs->flags >> 12) & 3; struct thread_struct *t = ¤t->thread; + /* + * Careful: the IOPL bits in regs->flags are undefined under Xen PV + * and changing them has no effect. + */ + unsigned int old = t->iopl >> 12; + if (level > 3) return -EINVAL; /* Trying to gain more privileges? */
