diff options
| author | Prarit Bhargava | 2013-11-12 15:08:33 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2013-11-13 12:09:11 +0900 |
| commit | 3d035f580699feba352f8703cced127fc203f0dd (patch) | |
| tree | 9469709ea2eda88e66531edb865ab41757615a0d /drivers/char | |
| parent | 72403b4a0fbdf433c1fe0127e49864658f6f6468 (diff) | |
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: Prarit Bhargava <prarit@redhat.com>
Acked-by: Matt Wilson <msw@amazon.com>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/Kconfig | 10 | ||||
| -rw-r--r-- | drivers/char/hpet.c | 24 |
2 files changed, 30 insertions, 4 deletions
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index 14219972c745..fa3243d71c76 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -522,10 +522,16 @@ config HPET_MMAP If you say Y here, user applications will be able to mmap 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 registers may also contain other things that shouldn't be - exposed to the user. If this applies to your hardware, - say N here. + exposed to the user. This option selects the default (if + kernel parameter hpet_mmap is not set) user access to the + registers for applications that require it. config HANGCHECK_TIMER tristate "Hangcheck timer" diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index dca5834685cf..5d9c31dfc905 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -367,12 +367,29 @@ static unsigned int hpet_poll(struct file *file, poll_table * wait) 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) { -#ifdef CONFIG_HPET_MMAP struct hpet_dev *devp; unsigned long addr; + if (!hpet_mmap_enabled) + return -EACCES; + devp = file->private_data; 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); return vm_iomap_memory(vma, addr, PAGE_SIZE); +} #else +static int hpet_mmap(struct file *file, struct vm_area_struct *vma) +{ return -ENOSYS; -#endif } +#endif static int hpet_fasync(int fd, struct file *file, int on) { |