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    Subject[PATCH 4.9 34/36] perf/x86/msr: Fix possible Spectre-v1 indexing in the MSR driver
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Peter Zijlstra <peterz@infradead.org>

    commit 06ce6e9b6d6c09d4129c6e24a1314a395d816c10 upstream.

    > arch/x86/events/msr.c:178 msr_event_init() warn: potential spectre issue 'msr' (local cap)

    Userspace controls @attr, sanitize cfg (attr->config) before using it
    to index an array.

    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: <stable@kernel.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/events/msr.c | 9 ++++++---
    1 file changed, 6 insertions(+), 3 deletions(-)

    --- a/arch/x86/events/msr.c
    +++ b/arch/x86/events/msr.c
    @@ -1,4 +1,5 @@
    #include <linux/perf_event.h>
    +#include <linux/nospec.h>
    #include <asm/intel-family.h>

    enum perf_msr_id {
    @@ -136,9 +137,6 @@ static int msr_event_init(struct perf_ev
    if (event->attr.type != event->pmu->type)
    return -ENOENT;

    - if (cfg >= PERF_MSR_EVENT_MAX)
    - return -EINVAL;
    -
    /* unsupported modes and filters */
    if (event->attr.exclude_user ||
    event->attr.exclude_kernel ||
    @@ -149,6 +147,11 @@ static int msr_event_init(struct perf_ev
    event->attr.sample_period) /* no sampling */
    return -EINVAL;

    + if (cfg >= PERF_MSR_EVENT_MAX)
    + return -EINVAL;
    +
    + cfg = array_index_nospec((unsigned long)cfg, PERF_MSR_EVENT_MAX);
    +
    if (!msr[cfg].attr)
    return -EINVAL;


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