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    Subject[PATCH 4.19 022/361] dma-mapping: fix panic caused by passing empty cma command line argument
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

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

    From: He Zhe <zhe.he@windriver.com>

    commit a3ceed87b07769fb80ce9dc6b604e515dba14c4b upstream.

    early_cma does not check input argument before passing it to
    simple_strtoull. The argument would be a NULL pointer if "cma", without
    its value, is set in command line and thus causes the following panic.

    PANIC: early exception 0xe3 IP 10:ffffffffa3e9db8d error 0 cr2 0x0
    [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc3-yocto-standard+ #7
    [ 0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
    ...
    [ 0.000000] Call Trace:
    [ 0.000000] simple_strtoull+0x29/0x70
    [ 0.000000] memparse+0x26/0x90
    [ 0.000000] early_cma+0x17/0x6a
    [ 0.000000] do_early_param+0x57/0x8e
    [ 0.000000] parse_args+0x208/0x320
    [ 0.000000] ? rdinit_setup+0x30/0x30
    [ 0.000000] parse_early_options+0x29/0x2d
    [ 0.000000] ? rdinit_setup+0x30/0x30
    [ 0.000000] parse_early_param+0x36/0x4d
    [ 0.000000] setup_arch+0x336/0x99e
    [ 0.000000] start_kernel+0x6f/0x4e6
    [ 0.000000] x86_64_start_reservations+0x24/0x26
    [ 0.000000] x86_64_start_kernel+0x6f/0x72
    [ 0.000000] secondary_startup_64+0xa4/0xb0

    This patch adds a check to prevent the panic.

    Signed-off-by: He Zhe <zhe.he@windriver.com>
    Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/dma/contiguous.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/kernel/dma/contiguous.c
    +++ b/kernel/dma/contiguous.c
    @@ -49,7 +49,11 @@ static phys_addr_t limit_cmdline;

    static int __init early_cma(char *p)
    {
    - pr_debug("%s(%s)\n", __func__, p);
    + if (!p) {
    + pr_err("Config string not provided\n");
    + return -EINVAL;
    + }
    +
    size_cmdline = memparse(p, &p);
    if (*p != '@')
    return 0;

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