Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3d035f58 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by Linus Torvalds
Browse files

drivers/char/hpet.c: allow user controlled mmap for user processes 



The CONFIG_HPET_MMAP Kconfig option exposes the memory map of the HPET
registers to userspace.  The Kconfig help points out that in some cases
this can be a security risk as some systems may erroneously configure the
map such that additional data is exposed to userspace.

This is a problem for distributions -- some users want the MMAP
functionality but it comes with a significant security risk.  In an effort
to mitigate this risk, and due to the low number of users of the MMAP
functionality, I've introduced a kernel parameter, hpet_mmap_enable, that
is required in order to actually have the HPET MMAP exposed.

Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Acked-by: default avatarMatt Wilson <msw@amazon.com>
Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 72403b4a

Documentation/kernel-parameters.txt

+3 −0
Original line number Original line Diff line number Diff line
@@ -1070,6 +1070,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
				VIA, nVidia)

				VIA, nVidia)

			verbose: show contents of HPET registers during setup

			verbose: show contents of HPET registers during setup





	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET

			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.



	hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.

	hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.

	hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.

	hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.

			On x86-64 and powerpc, this option can be specified

			On x86-64 and powerpc, this option can be specified

drivers/char/Kconfig

+8 −2
Original line number Original line Diff line number Diff line
@@ -522,10 +522,16 @@ config HPET_MMAP 
	  If you say Y here, user applications will be able to mmap

	  If you say Y here, user applications will be able to mmap

	  the HPET registers.

	  the HPET registers.





config HPET_MMAP_DEFAULT

	bool "Enable HPET MMAP access by default"

	default y

	depends on HPET_MMAP

	help

	  In some hardware implementations, the page containing HPET

	  In some hardware implementations, the page containing HPET

	  registers may also contain other things that shouldn't be

	  registers may also contain other things that shouldn't be

	  exposed to the user.  If this applies to your hardware,

	  exposed to the user.  This option selects the default (if

	  say N here.

	  kernel parameter hpet_mmap is not set) user access to the

	  registers for applications that require it.





config HANGCHECK_TIMER

config HANGCHECK_TIMER

	tristate "Hangcheck timer"

	tristate "Hangcheck timer"

drivers/char/hpet.c

+22 −2
Original line number Original line Diff line number Diff line
@@ -367,12 +367,29 @@ static unsigned int hpet_poll(struct file *file, poll_table * wait) 
	return 0;

	return 0;

}

}





#ifdef CONFIG_HPET_MMAP

#ifdef CONFIG_HPET_MMAP_DEFAULT

static int hpet_mmap_enabled = 1;

#else

static int hpet_mmap_enabled = 0;

#endif



static __init int hpet_mmap_enable(char *str)

{

	get_option(&str, &hpet_mmap_enabled);

	pr_info("HPET mmap %s\n", hpet_mmap_enabled ? "enabled" : "disabled");

	return 1;

}

__setup("hpet_mmap", hpet_mmap_enable);



static int hpet_mmap(struct file *file, struct vm_area_struct *vma)

static int hpet_mmap(struct file *file, struct vm_area_struct *vma)

{

{

#ifdef	CONFIG_HPET_MMAP

	struct hpet_dev *devp;

	struct hpet_dev *devp;

	unsigned long addr;

	unsigned long addr;





	if (!hpet_mmap_enabled)

		return -EACCES;



	devp = file->private_data;

	devp = file->private_data;

	addr = devp->hd_hpets->hp_hpet_phys;

	addr = devp->hd_hpets->hp_hpet_phys;
@@ -381,10 +398,13 @@ static int hpet_mmap(struct file *file, struct vm_area_struct *vma) 




	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

	return vm_iomap_memory(vma, addr, PAGE_SIZE);

	return vm_iomap_memory(vma, addr, PAGE_SIZE);

}

#else

#else

static int hpet_mmap(struct file *file, struct vm_area_struct *vma)

{

	return -ENOSYS;

	return -ENOSYS;

#endif

}

}

#endif





static int hpet_fasync(int fd, struct file *file, int on)

static int hpet_fasync(int fd, struct file *file, int on)

{

{