1. 07 Jan, 2019 32 commits
  2. 06 Jan, 2019 8 commits
    • Linus Torvalds's avatar
      Change mincore() to count "mapped" pages rather than "cached" pages · 574823bf
      Linus Torvalds authored
      The semantics of what "in core" means for the mincore() system call are
      somewhat unclear, but Linux has always (since 2.3.52, which is when
      mincore() was initially done) treated it as "page is available in page
      cache" rather than "page is mapped in the mapping".
      
      The problem with that traditional semantic is that it exposes a lot of
      system cache state that it really probably shouldn't, and that users
      shouldn't really even care about.
      
      So let's try to avoid that information leak by simply changing the
      semantics to be that mincore() counts actual mapped pages, not pages
      that might be cheaply mapped if they were faulted (note the "might be"
      part of the old semantics: being in the cache doesn't actually guarantee
      that you can access them without IO anyway, since things like network
      filesystems may have to revalidate the cache before use).
      
      In many ways the old semantics were somewhat insane even aside from the
      information leak issue.  From the very beginning (and that beginning is
      a long time ago: 2.3.52 was released in March 2000, I think), the code
      had a comment saying
      
        Later we can get more picky about what "in core" means precisely.
      
      and this is that "later".  Admittedly it is much later than is really
      comfortable.
      
      NOTE! This is a real semantic change, and it is for example known to
      change the output of "fincore", since that program literally does a
      mmmap without populating it, and then doing "mincore()" on that mapping
      that doesn't actually have any pages in it.
      
      I'm hoping that nobody actually has any workflow that cares, and the
      info leak is real.
      
      We may have to do something different if it turns out that people have
      valid reasons to want the old semantics, and if we can limit the
      information leak sanely.
      
      Cc: Kevin Easton <kevin@guarana.org>
      Cc: Jiri Kosina <jikos@kernel.org>
      Cc: Masatake YAMATO <yamato@redhat.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Greg KH <gregkh@linuxfoundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Michal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      574823bf
    • Linus Torvalds's avatar
      Fix 'acccess_ok()' on alpha and SH · 94bd8a05
      Linus Torvalds authored
      Commit 594cc251 ("make 'user_access_begin()' do 'access_ok()'")
      broke both alpha and SH booting in qemu, as noticed by Guenter Roeck.
      
      It turns out that the bug wasn't actually in that commit itself (which
      would have been surprising: it was mostly a no-op), but in how the
      addition of access_ok() to the strncpy_from_user() and strnlen_user()
      functions now triggered the case where those functions would test the
      access of the very last byte of the user address space.
      
      The string functions actually did that user range test before too, but
      they did it manually by just comparing against user_addr_max().  But
      with user_access_begin() doing the check (using "access_ok()"), it now
      exposed problems in the architecture implementations of that function.
      
      For example, on alpha, the access_ok() helper macro looked like this:
      
        #define __access_ok(addr, size) \
              ((get_fs().seg & (addr | size | (addr+size))) == 0)
      
      and what it basically tests is of any of the high bits get set (the
      USER_DS masking value is 0xfffffc0000000000).
      
      And that's completely wrong for the "addr+size" check.  Because it's
      off-by-one for the case where we check to the very end of the user
      address space, which is exactly what the strn*_user() functions do.
      
      Why? Because "addr+size" will be exactly the size of the address space,
      so trying to access the last byte of the user address space will fail
      the __access_ok() check, even though it shouldn't.  As a result, the
      user string accessor functions failed consistently - because they
      literally don't know how long the string is going to be, and the max
      access is going to be that last byte of the user address space.
      
      Side note: that alpha macro is buggy for another reason too - it re-uses
      the arguments twice.
      
      And SH has another version of almost the exact same bug:
      
        #define __addr_ok(addr) \
              ((unsigned long __force)(addr) < current_thread_info()->addr_limit.seg)
      
      so far so good: yes, a user address must be below the limit.  But then:
      
        #define __access_ok(addr, size)         \
              (__addr_ok((addr) + (size)))
      
      is wrong with the exact same off-by-one case: the case when "addr+size"
      is exactly _equal_ to the limit is actually perfectly fine (think "one
      byte access at the last address of the user address space")
      
      The SH version is actually seriously buggy in another way: it doesn't
      actually check for overflow, even though it did copy the _comment_ that
      talks about overflow.
      
      So it turns out that both SH and alpha actually have completely buggy
      implementations of access_ok(), but they happened to work in practice
      (although the SH overflow one is a serious serious security bug, not
      that anybody likely cares about SH security).
      
      This fixes the problems by using a similar macro on both alpha and SH.
      It isn't trying to be clever, the end address is based on this logic:
      
              unsigned long __ao_end = __ao_a + __ao_b - !!__ao_b;
      
      which basically says "add start and length, and then subtract one unless
      the length was zero".  We can't subtract one for a zero length, or we'd
      just hit an underflow instead.
      
      For a lot of access_ok() users the length is a constant, so this isn't
      actually as expensive as it initially looks.
      Reported-and-tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
      Cc: Matt Turner <mattst88@gmail.com>
      Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      94bd8a05
    • Linus Torvalds's avatar
      Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt · baa67073
      Linus Torvalds authored
      Pull fscrypt updates from Ted Ts'o:
       "Add Adiantum support for fscrypt"
      
      * tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt:
        fscrypt: add Adiantum support
      baa67073
    • Linus Torvalds's avatar
      Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 · 21524046
      Linus Torvalds authored
      Pull ext4 bug fixes from Ted Ts'o:
       "Fix a number of ext4 bugs"
      
      * tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
        ext4: fix special inode number checks in __ext4_iget()
        ext4: track writeback errors using the generic tracking infrastructure
        ext4: use ext4_write_inode() when fsyncing w/o a journal
        ext4: avoid kernel warning when writing the superblock to a dead device
        ext4: fix a potential fiemap/page fault deadlock w/ inline_data
        ext4: make sure enough credits are reserved for dioread_nolock writes
      21524046
    • Linus Torvalds's avatar
      Merge tag 'dma-mapping-4.21-1' of git://git.infradead.org/users/hch/dma-mapping · e2b745f4
      Linus Torvalds authored
      Pull dma-mapping fixes from Christoph Hellwig:
       "Fix various regressions introduced in this cycles:
      
         - fix dma-debug tracking for the map_page / map_single
           consolidatation
      
         - properly stub out DMA mapping symbols for !HAS_DMA builds to avoid
           link failures
      
         - fix AMD Gart direct mappings
      
         - setup the dma address for no kernel mappings using the remap
           allocator"
      
      * tag 'dma-mapping-4.21-1' of git://git.infradead.org/users/hch/dma-mapping:
        dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING for remapped allocations
        x86/amd_gart: fix unmapping of non-GART mappings
        dma-mapping: remove a few unused exports
        dma-mapping: properly stub out the DMA API for !CONFIG_HAS_DMA
        dma-mapping: remove dmam_{declare,release}_coherent_memory
        dma-mapping: implement dmam_alloc_coherent using dmam_alloc_attrs
        dma-mapping: implement dma_map_single_attrs using dma_map_page_attrs
      e2b745f4
    • Linus Torvalds's avatar
      Merge tag 'tag-chrome-platform-for-v4.21' of... · 12133258
      Linus Torvalds authored
      Merge tag 'tag-chrome-platform-for-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/bleung/chrome-platform
      
      Pull chrome platform updates from Benson Leung:
      
       - Changes for EC_MKBP_EVENT_SENSOR_FIFO handling.
      
       - Also, maintainership changes. Olofj out, Enric balletbo in.
      
      * tag 'tag-chrome-platform-for-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/bleung/chrome-platform:
        MAINTAINERS: add maintainers for ChromeOS EC sub-drivers
        MAINTAINERS: platform/chrome: Add Enric as a maintainer
        MAINTAINERS: platform/chrome: remove myself as maintainer
        platform/chrome: don't report EC_MKBP_EVENT_SENSOR_FIFO as wakeup
        platform/chrome: straighten out cros_ec_get_{next,host}_event() error codes
      12133258
    • Linus Torvalds's avatar
      Merge tag 'hwlock-v4.21' of git://github.com/andersson/remoteproc · 66e012f6
      Linus Torvalds authored
      Pull hwspinlock updates from Bjorn Andersson:
       "This adds support for the hardware semaphores found in STM32MP1"
      
      * tag 'hwlock-v4.21' of git://github.com/andersson/remoteproc:
        hwspinlock: fix return value check in stm32_hwspinlock_probe()
        hwspinlock: add STM32 hwspinlock device
        dt-bindings: hwlock: Document STM32 hwspinlock bindings
      66e012f6
    • Eric Biggers's avatar
      fscrypt: add Adiantum support · 8094c3ce
      Eric Biggers authored
      Add support for the Adiantum encryption mode to fscrypt.  Adiantum is a
      tweakable, length-preserving encryption mode with security provably
      reducible to that of XChaCha12 and AES-256, subject to a security bound.
      It's also a true wide-block mode, unlike XTS.  See the paper
      "Adiantum: length-preserving encryption for entry-level processors"
      (https://eprint.iacr.org/2018/720.pdf) for more details.  Also see
      commit 059c2a4d ("crypto: adiantum - add Adiantum support").
      
      On sufficiently long messages, Adiantum's bottlenecks are XChaCha12 and
      the NH hash function.  These algorithms are fast even on processors
      without dedicated crypto instructions.  Adiantum makes it feasible to
      enable storage encryption on low-end mobile devices that lack AES
      instructions; currently such devices are unencrypted.  On ARM Cortex-A7,
      on 4096-byte messages Adiantum encryption is about 4 times faster than
      AES-256-XTS encryption; decryption is about 5 times faster.
      
      In fscrypt, Adiantum is suitable for encrypting both file contents and
      names.  With filenames, it fixes a known weakness: when two filenames in
      a directory share a common prefix of >= 16 bytes, with CTS-CBC their
      encrypted filenames share a common prefix too, leaking information.
      Adiantum does not have this problem.
      
      Since Adiantum also accepts long tweaks (IVs), it's also safe to use the
      master key directly for Adiantum encryption rather than deriving
      per-file keys, provided that the per-file nonce is included in the IVs
      and the master key isn't used for any other encryption mode.  This
      configuration saves memory and improves performance.  A new fscrypt
      policy flag is added to allow users to opt-in to this configuration.
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
      8094c3ce