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    Subject[PATCH 3.14 085/110] x86-32, espfix: Remove filter for espfix32 due to race
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "H. Peter Anvin" <hpa@linux.intel.com>

    commit 246f2d2ee1d715e1077fc47d61c394569c8ee692 upstream.

    It is not safe to use LAR to filter when to go down the espfix path,
    because the LDT is per-process (rather than per-thread) and another
    thread might change the descriptors behind our back. Fortunately it
    is always *safe* (if a bit slow) to go down the espfix path, and a
    32-bit LDT stack segment is extremely rare.

    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/entry_32.S | 5 -----
    1 file changed, 5 deletions(-)

    --- a/arch/x86/kernel/entry_32.S
    +++ b/arch/x86/kernel/entry_32.S
    @@ -551,11 +551,6 @@ ENTRY(iret_exc)

    CFI_RESTORE_STATE
    ldt_ss:
    - larl PT_OLDSS(%esp), %eax
    - jnz restore_nocheck
    - testl $0x00400000, %eax # returning to 32bit stack?
    - jnz restore_nocheck # allright, normal return
    -
    #ifdef CONFIG_PARAVIRT
    /*
    * The kernel can't run on a non-flat stack if paravirt mode



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