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    Subject[PATCH 5.0 240/346] x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP
    Date
    [ Upstream commit 4a6c91fbdef846ec7250b82f2eeeb87ac5f18cf9 ]

    For CONFIG_TRACE_BRANCH_PROFILING=y the likely/unlikely things get
    overloaded and generate callouts to this code, and thus also when
    AC=1.

    Make it safe.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/trace/trace_branch.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
    index 4ad967453b6fb..3ea65cdff30d5 100644
    --- a/kernel/trace/trace_branch.c
    +++ b/kernel/trace/trace_branch.c
    @@ -205,6 +205,8 @@ void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
    void ftrace_likely_update(struct ftrace_likely_data *f, int val,
    int expect, int is_constant)
    {
    + unsigned long flags = user_access_save();
    +
    /* A constant is always correct */
    if (is_constant) {
    f->constant++;
    @@ -223,6 +225,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
    f->data.correct++;
    else
    f->data.incorrect++;
    +
    + user_access_restore(flags);
    }
    EXPORT_SYMBOL(ftrace_likely_update);

    --
    2.20.1


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