1. 03 6月, 2017 18 次提交
  2. 27 5月, 2017 1 次提交
  3. 26 5月, 2017 7 次提交
  4. 25 5月, 2017 11 次提交
  5. 22 5月, 2017 3 次提交
    • G
      Merge 4.12-rc2 into char-misc-next · b4a338d2
      Greg Kroah-Hartman 提交于
      We want the fixes in here as well to handle merge issues.
      Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b4a338d2
    • L
      Linux 4.12-rc2 · 08332893
      Linus Torvalds 提交于
      08332893
    • L
      x86: fix 32-bit case of __get_user_asm_u64() · 33c9e972
      Linus Torvalds 提交于
      The code to fetch a 64-bit value from user space was entirely buggered,
      and has been since the code was merged in early 2016 in commit
      b2f68038 ("x86/mm/32: Add support for 64-bit __get_user() on 32-bit
      kernels").
      
      Happily the buggered routine is almost certainly entirely unused, since
      the normal way to access user space memory is just with the non-inlined
      "get_user()", and the inlined version didn't even historically exist.
      
      The normal "get_user()" case is handled by external hand-written asm in
      arch/x86/lib/getuser.S that doesn't have either of these issues.
      
      There were two independent bugs in __get_user_asm_u64():
      
       - it still did the STAC/CLAC user space access marking, even though
         that is now done by the wrapper macros, see commit 11f1a4b9
         ("x86: reorganize SMAP handling in user space accesses").
      
         This didn't result in a semantic error, it just means that the
         inlined optimized version was hugely less efficient than the
         allegedly slower standard version, since the CLAC/STAC overhead is
         quite high on modern Intel CPU's.
      
       - the double register %eax/%edx was marked as an output, but the %eax
         part of it was touched early in the asm, and could thus clobber other
         inputs to the asm that gcc didn't expect it to touch.
      
         In particular, that meant that the generated code could look like
         this:
      
              mov    (%eax),%eax
              mov    0x4(%eax),%edx
      
         where the load of %edx obviously was _supposed_ to be from the 32-bit
         word that followed the source of %eax, but because %eax was
         overwritten by the first instruction, the source of %edx was
         basically random garbage.
      
      The fixes are trivial: remove the extraneous STAC/CLAC entries, and mark
      the 64-bit output as early-clobber to let gcc know that no inputs should
      alias with the output register.
      
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Benjamin LaHaise <bcrl@kvack.org>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: stable@kernel.org   # v4.8+
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      33c9e972