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    Subject[PATCH 4.19 003/101] powerpc/tm: Limit TM code inside PPC_TRANSACTIONAL_MEM
    Date
    commit 897bc3df8c5aebb54c32d831f917592e873d0559 upstream.

    Commit e1c3743e1a20 ("powerpc/tm: Set MSR[TS] just prior to recheckpoint")
    moved a code block around and this block uses a 'msr' variable outside of
    the CONFIG_PPC_TRANSACTIONAL_MEM, however the 'msr' variable is declared
    inside a CONFIG_PPC_TRANSACTIONAL_MEM block, causing a possible error when
    CONFIG_PPC_TRANSACTION_MEM is not defined.

    error: 'msr' undeclared (first use in this function)

    This is not causing a compilation error in the mainline kernel, because
    'msr' is being used as an argument of MSR_TM_ACTIVE(), which is defined as
    the following when CONFIG_PPC_TRANSACTIONAL_MEM is *not* set:

    #define MSR_TM_ACTIVE(x) 0

    This patch just fixes this issue avoiding the 'msr' variable usage outside
    the CONFIG_PPC_TRANSACTIONAL_MEM block, avoiding trusting in the
    MSR_TM_ACTIVE() definition.

    Cc: stable@vger.kernel.org
    Reported-by: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
    Fixes: e1c3743e1a20 ("powerpc/tm: Set MSR[TS] just prior to recheckpoint")
    Signed-off-by: Breno Leitao <leitao@debian.org>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Michael Neuling <mikey@neuling.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/signal_64.c | 23 ++++++++++++++++++-----
    1 file changed, 18 insertions(+), 5 deletions(-)

    diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
    index bbd1c73243d7..14b0f5b6a373 100644
    --- a/arch/powerpc/kernel/signal_64.c
    +++ b/arch/powerpc/kernel/signal_64.c
    @@ -755,12 +755,25 @@ SYSCALL_DEFINE0(rt_sigreturn)
    if (restore_tm_sigcontexts(current, &uc->uc_mcontext,
    &uc_transact->uc_mcontext))
    goto badframe;
    - }
    - else
    - /* Fall through, for non-TM restore */
    + } else
    #endif
    - if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
    - goto badframe;
    + {
    + /*
    + * Fall through, for non-TM restore
    + *
    + * Unset MSR[TS] on the thread regs since MSR from user
    + * context does not have MSR active, and recheckpoint was
    + * not called since restore_tm_sigcontexts() was not called
    + * also.
    + *
    + * If not unsetting it, the code can RFID to userspace with
    + * MSR[TS] set, but without CPU in the proper state,
    + * causing a TM bad thing.
    + */
    + current->thread.regs->msr &= ~MSR_TS_MASK;
    + if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
    + goto badframe;
    + }

    if (restore_altstack(&uc->uc_stack))
    goto badframe;
    --
    2.19.1


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