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    Subject[PATCH 5.10 434/599] kdb: Fix the putarea helper function
    Date
    From: Daniel Thompson <daniel.thompson@linaro.org>

    [ Upstream commit c1cb81429df462eca1b6ba615cddd21dd3103c46 ]

    Currently kdb_putarea_size() uses copy_from_kernel_nofault() to write *to*
    arbitrary kernel memory. This is obviously wrong and means the memory
    modify ('mm') command is a serious risk to debugger stability: if we poke
    to a bad address we'll double-fault and lose our debug session.

    Fix this the (very) obvious way.

    Note that there are two Fixes: tags because the API was renamed and this
    patch will only trivially backport as far as the rename (and this is
    probably enough). Nevertheless Christoph's rename did not introduce this
    problem so I wanted to record that!

    Fixes: fe557319aa06 ("maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault")
    Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
    Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
    Reviewed-by: Douglas Anderson <dianders@chromium.org>
    Link: https://lore.kernel.org/r/20220128144055.207267-1-daniel.thompson@linaro.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/debug/kdb/kdb_support.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
    index 6226502ce049..13417f0045f0 100644
    --- a/kernel/debug/kdb/kdb_support.c
    +++ b/kernel/debug/kdb/kdb_support.c
    @@ -350,7 +350,7 @@ int kdb_getarea_size(void *res, unsigned long addr, size_t size)
    */
    int kdb_putarea_size(unsigned long addr, void *res, size_t size)
    {
    - int ret = copy_from_kernel_nofault((char *)addr, (char *)res, size);
    + int ret = copy_to_kernel_nofault((char *)addr, (char *)res, size);
    if (ret) {
    if (!KDB_STATE(SUPPRESS)) {
    kdb_printf("kdb_putarea: Bad address 0x%lx\n", addr);
    --
    2.34.1


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