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    Subject[PATCH 4.19 369/639] kdb: do a sanity check on the cpu in kdb_per_cpu()
    Date
    From: Dan Carpenter <dan.carpenter@oracle.com>

    [ Upstream commit b586627e10f57ee3aa8f0cfab0d6f7dc4ae63760 ]

    The "whichcpu" comes from argv[3]. The cpu_online() macro looks up the
    cpu in a bitmap of online cpus, but if the value is too high then it
    could read beyond the end of the bitmap and possibly Oops.

    Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
    Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    Reviewed-by: Douglas Anderson <dianders@chromium.org>
    Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/debug/kdb/kdb_main.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
    index f338d23b112b5..dc6bf35e78840 100644
    --- a/kernel/debug/kdb/kdb_main.c
    +++ b/kernel/debug/kdb/kdb_main.c
    @@ -2604,7 +2604,7 @@ static int kdb_per_cpu(int argc, const char **argv)
    diag = kdbgetularg(argv[3], &whichcpu);
    if (diag)
    return diag;
    - if (!cpu_online(whichcpu)) {
    + if (whichcpu >= nr_cpu_ids || !cpu_online(whichcpu)) {
    kdb_printf("cpu %ld is not online\n", whichcpu);
    return KDB_BADCPUNUM;
    }
    --
    2.20.1


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