Re: [PATCH 13/24] x86: Lock down IO port access when the kernel is locked down

[Thomas Gleixner]

On Wed, 5 Apr 2017, David Howells wrote:
> From: Matthew Garrett 
> 
> IO port access would permit users to gain access to PCI configuration
> registers, which in turn (on a lot of hardware) give access to MMIO
> register space. This would potentially permit root to trigger arbitrary
> DMA, so lock it down by default.
> 
> This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
> KDDISABIO console ioctls.
> 
> Signed-off-by: Matthew Garrett 
> Signed-off-by: David Howells 

Reviewed-by: Thomas Gleixner 
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[PATCH 13/24] x86: Lock down IO port access when the kernel is locked down

[David Howells]

From: Matthew Garrett 

IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.

This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.

Signed-off-by: Matthew Garrett 
Signed-off-by: David Howells 
cc: x...@kernel.org
---

 arch/x86/kernel/ioport.c |4 ++--
 drivers/char/mem.c   |2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9c3cf0944bce..4a613fed94b6 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,7 +30,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long 
num, int turn_on)
 
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
-   if (turn_on && !capable(CAP_SYS_RAWIO))
+   if (turn_on && (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down()))
return -EPERM;
 
/*
@@ -120,7 +120,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
return -EINVAL;
/* Trying to gain more privileges? */
if (level > old) {
-   if (!capable(CAP_SYS_RAWIO))
+   if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
return -EPERM;
}
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f8144049bda3..9afebb60550f 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -741,6 +741,8 @@ static loff_t memory_lseek(struct file *file, loff_t 
offset, int orig)
 
 static int open_port(struct inode *inode, struct file *filp)
 {
+   if (kernel_is_locked_down())
+   return -EPERM;
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 

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[PATCH 13/24] x86: Lock down IO port access when the kernel is locked down

[David Howells]

From: Matthew Garrett 

IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.

This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.

Signed-off-by: Matthew Garrett 
Signed-off-by: David Howells 
---

 arch/x86/kernel/ioport.c |4 ++--
 drivers/char/mem.c   |2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9c3cf0944bce..4a613fed94b6 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,7 +30,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long 
num, int turn_on)
 
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
-   if (turn_on && !capable(CAP_SYS_RAWIO))
+   if (turn_on && (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down()))
return -EPERM;
 
/*
@@ -120,7 +120,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
return -EINVAL;
/* Trying to gain more privileges? */
if (level > old) {
-   if (!capable(CAP_SYS_RAWIO))
+   if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
return -EPERM;
}
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f8144049bda3..9afebb60550f 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -741,6 +741,8 @@ static loff_t memory_lseek(struct file *file, loff_t 
offset, int orig)
 
 static int open_port(struct inode *inode, struct file *filp)
 {
+   if (kernel_is_locked_down())
+   return -EPERM;
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 

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