This is a note to let you know that I've just added the patch titled
x86/iopl: Fix iopl capability check on Xen PV
to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-iopl-fix-iopl-capability-check-on-xen-pv.patch
and it can be found in the queue-4.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c29016cf41fe9fa994a5ecca607cf5f1cd98801e Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@xxxxxxxxxx>
Date: Wed, 16 Mar 2016 14:14:22 -0700
Subject: x86/iopl: Fix iopl capability check on Xen PV
From: Andy Lutomirski <luto@xxxxxxxxxx>
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 <JBeulich@xxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/8ce12013e6e4c0a44a97e316be4a6faff31bd5ea.1458162709.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long
SYSCALL_DEFINE1(iopl, unsigned int, level)
{
struct pt_regs *regs = current_pt_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 >> X86_EFLAGS_IOPL_BIT;
+
if (level > 3)
return -EINVAL;
/* Trying to gain more privileges? */
@@ -106,8 +111,9 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
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;
Patches currently in stable-queue which might be from luto@xxxxxxxxxx are
queue-4.5/x86-iopl-64-properly-context-switch-iopl-on-xen-pv.patch
queue-4.5/x86-iopl-fix-iopl-capability-check-on-xen-pv.patch
queue-4.5/x86-entry-compat-keep-ts_compat-set-during-signal-delivery.patch
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