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    Subject[PATCH 5.15 118/135] powerpc/rtas: Allow ibm,platform-dump RTAS call with null buffer address
    Date
    From: Andrew Donnellan <ajd@linux.ibm.com>

    commit 7bc08056a6dabc3a1442216daf527edf61ac24b6 upstream.

    Add a special case to block_rtas_call() to allow the ibm,platform-dump RTAS
    call through the RTAS filter if the buffer address is 0.

    According to PAPR, ibm,platform-dump is called with a null buffer address
    to notify the platform firmware that processing of a particular dump is
    finished.

    Without this, on a pseries machine with CONFIG_PPC_RTAS_FILTER enabled, an
    application such as rtas_errd that is attempting to retrieve a dump will
    encounter an error at the end of the retrieval process.

    Fixes: bd59380c5ba4 ("powerpc/rtas: Restrict RTAS requests from userspace")
    Cc: stable@vger.kernel.org
    Reported-by: Sathvika Vasireddy <sathvika@linux.ibm.com>
    Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
    Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
    Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20220614134952.156010-1-ajd@linux.ibm.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/powerpc/kernel/rtas.c | 11 ++++++++++-
    1 file changed, 10 insertions(+), 1 deletion(-)

    --- a/arch/powerpc/kernel/rtas.c
    +++ b/arch/powerpc/kernel/rtas.c
    @@ -983,7 +983,7 @@ static struct rtas_filter rtas_filters[]
    { "get-time-of-day", -1, -1, -1, -1, -1 },
    { "ibm,get-vpd", -1, 0, -1, 1, 2 },
    { "ibm,lpar-perftools", -1, 2, 3, -1, -1 },
    - { "ibm,platform-dump", -1, 4, 5, -1, -1 },
    + { "ibm,platform-dump", -1, 4, 5, -1, -1 }, /* Special cased */
    { "ibm,read-slot-reset-state", -1, -1, -1, -1, -1 },
    { "ibm,scan-log-dump", -1, 0, 1, -1, -1 },
    { "ibm,set-dynamic-indicator", -1, 2, -1, -1, -1 },
    @@ -1032,6 +1032,15 @@ static bool block_rtas_call(int token, i
    size = 1;

    end = base + size - 1;
    +
    + /*
    + * Special case for ibm,platform-dump - NULL buffer
    + * address is used to indicate end of dump processing
    + */
    + if (!strcmp(f->name, "ibm,platform-dump") &&
    + base == 0)
    + return false;
    +
    if (!in_rmo_buf(base, end))
    goto err;
    }

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