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    Subject[PATCH 4.17 216/220] x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80"
    Date
    4.17-stable review patch.  If anyone has any objections, please let me know.

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

    From: Andy Lutomirski <luto@kernel.org>

    commit 22cd978e598618e82c3c3348d2069184f6884182 upstream.

    Commit:

    8bb2610bc496 ("x86/entry/64/compat: Preserve r8-r11 in int $0x80")

    was busted: my original patch had a minor conflict with
    some of the nospec changes, but "git apply" is very clever
    and silently accepted the patch by making the same changes
    to a different function in the same file. There was obviously
    a huge offset, but "git apply" for some reason doesn't feel
    any need to say so.

    Move the changes to the correct function. Now the
    test_syscall_vdso_32 selftests passes.

    If anyone cares to observe the original problem, try applying the
    patch at:

    https://lore.kernel.org/lkml/d4c4d9985fbe64f8c9e19291886453914b48caee.1523975710.git.luto@kernel.org/raw

    to the kernel at 316d097c4cd4e7f2ef50c40cff2db266593c4ec4:

    - "git am" and "git apply" accept the patch without any complaints at all
    - "patch -p1" at least prints out a message about the huge offset.

    Reported-by: zhijianx.li@intel.com
    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David Woodhouse <dwmw2@infradead.org>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: stable@vger.kernel.org #v4.17+
    Fixes: 8bb2610bc496 ("x86/entry/64/compat: Preserve r8-r11 in int $0x80")
    Link: http://lkml.kernel.org/r/6012b922485401bc42676e804171ded262fc2ef2.1530078306.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/entry/entry_64_compat.S | 16 ++++++++--------
    1 file changed, 8 insertions(+), 8 deletions(-)

    --- a/arch/x86/entry/entry_64_compat.S
    +++ b/arch/x86/entry/entry_64_compat.S
    @@ -84,13 +84,13 @@ ENTRY(entry_SYSENTER_compat)
    pushq %rdx /* pt_regs->dx */
    pushq %rcx /* pt_regs->cx */
    pushq $-ENOSYS /* pt_regs->ax */
    - pushq %r8 /* pt_regs->r8 */
    + pushq $0 /* pt_regs->r8 = 0 */
    xorl %r8d, %r8d /* nospec r8 */
    - pushq %r9 /* pt_regs->r9 */
    + pushq $0 /* pt_regs->r9 = 0 */
    xorl %r9d, %r9d /* nospec r9 */
    - pushq %r10 /* pt_regs->r10 */
    + pushq $0 /* pt_regs->r10 = 0 */
    xorl %r10d, %r10d /* nospec r10 */
    - pushq %r11 /* pt_regs->r11 */
    + pushq $0 /* pt_regs->r11 = 0 */
    xorl %r11d, %r11d /* nospec r11 */
    pushq %rbx /* pt_regs->rbx */
    xorl %ebx, %ebx /* nospec rbx */
    @@ -374,13 +374,13 @@ ENTRY(entry_INT80_compat)
    pushq %rcx /* pt_regs->cx */
    xorl %ecx, %ecx /* nospec cx */
    pushq $-ENOSYS /* pt_regs->ax */
    - pushq $0 /* pt_regs->r8 = 0 */
    + pushq %r8 /* pt_regs->r8 */
    xorl %r8d, %r8d /* nospec r8 */
    - pushq $0 /* pt_regs->r9 = 0 */
    + pushq %r9 /* pt_regs->r9 */
    xorl %r9d, %r9d /* nospec r9 */
    - pushq $0 /* pt_regs->r10 = 0 */
    + pushq %r10 /* pt_regs->r10*/
    xorl %r10d, %r10d /* nospec r10 */
    - pushq $0 /* pt_regs->r11 = 0 */
    + pushq %r11 /* pt_regs->r11 */
    xorl %r11d, %r11d /* nospec r11 */
    pushq %rbx /* pt_regs->rbx */
    xorl %ebx, %ebx /* nospec rbx */

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