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The patch protects from leaking sensitive data after resume from suspend. During suspend a temporary key is created and this key is used to encrypt the data written to disk. When, during resume, the data was read back into memory the temporary key is destroyed which simply means that all data written to disk during suspend are then inaccessible so they can't be stolen lateron. Think of the following: you suspend while an application is running that keeps sensitive data in memory. The application itself prevents the data from being swapped out. Suspend, however, must write these data to swap to be able to resume lateron. Without suspend encryption your sensitive data are then stored in plaintext on disk. This means that after resume your sensitive data are accessible to all applications having direct access to the swap device which was used for suspend. If you don't need swap after resume these data can remain on disk virtually forever. Thus it can happen that your system gets broken in weeks later and sensitive data which you thought were encrypted and protected are retrieved and stolen from the swap device. Signed-off-by: Andreas Steinmetz <ast@domdv.de> Acked-by: Pavel Machek <pavel@suse.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
90 lines
3.4 KiB
Text
90 lines
3.4 KiB
Text
config PM
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bool "Power Management support"
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---help---
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"Power Management" means that parts of your computer are shut
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off or put into a power conserving "sleep" mode if they are not
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being used. There are two competing standards for doing this: APM
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and ACPI. If you want to use either one, say Y here and then also
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to the requisite support below.
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Power Management is most important for battery powered laptop
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computers; if you have a laptop, check out the Linux Laptop home
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page on the WWW at <http://www.linux-on-laptops.com/> or
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Tuxmobil - Linux on Mobile Computers at <http://www.tuxmobil.org/>
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and the Battery Powered Linux mini-HOWTO, available from
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<http://www.tldp.org/docs.html#howto>.
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Note that, even if you say N here, Linux on the x86 architecture
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will issue the hlt instruction if nothing is to be done, thereby
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sending the processor to sleep and saving power.
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config PM_DEBUG
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bool "Power Management Debug Support"
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depends on PM
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---help---
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This option enables verbose debugging support in the Power Management
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code. This is helpful when debugging and reporting various PM bugs,
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like suspend support.
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config SOFTWARE_SUSPEND
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bool "Software Suspend"
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depends on EXPERIMENTAL && PM && SWAP && ((X86 && SMP) || ((FVR || PPC32 || X86) && !SMP))
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---help---
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Enable the possibility of suspending the machine.
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It doesn't need APM.
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You may suspend your machine by 'swsusp' or 'shutdown -z <time>'
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(patch for sysvinit needed).
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It creates an image which is saved in your active swap. Upon next
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boot, pass the 'resume=/dev/swappartition' argument to the kernel to
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have it detect the saved image, restore memory state from it, and
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continue to run as before. If you do not want the previous state to
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be reloaded, then use the 'noresume' kernel argument. However, note
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that your partitions will be fsck'd and you must re-mkswap your swap
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partitions. It does not work with swap files.
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Right now you may boot without resuming and then later resume but
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in meantime you cannot use those swap partitions/files which were
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involved in suspending. Also in this case there is a risk that buffers
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on disk won't match with saved ones.
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For more information take a look at <file:Documentation/power/swsusp.txt>.
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config PM_STD_PARTITION
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string "Default resume partition"
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depends on SOFTWARE_SUSPEND
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default ""
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---help---
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The default resume partition is the partition that the suspend-
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to-disk implementation will look for a suspended disk image.
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The partition specified here will be different for almost every user.
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It should be a valid swap partition (at least for now) that is turned
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on before suspending.
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The partition specified can be overridden by specifying:
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resume=/dev/<other device>
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which will set the resume partition to the device specified.
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Note there is currently not a way to specify which device to save the
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suspended image to. It will simply pick the first available swap
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device.
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config SWSUSP_ENCRYPT
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bool "Encrypt suspend image"
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depends on SOFTWARE_SUSPEND && CRYPTO=y && (CRYPTO_AES=y || CRYPTO_AES_586=y || CRYPTO_AES_X86_64=y)
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default ""
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---help---
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To prevent data gathering from swap after resume you can encrypt
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the suspend image with a temporary key that is deleted on
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resume.
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Note that the temporary key is stored unencrypted on disk while the
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system is suspended.
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config SUSPEND_SMP
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bool
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depends on HOTPLUG_CPU && X86 && PM
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default y
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