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    Subject[PATCH 4.19 266/346] Input: cyapa_gen6 - fix out-of-bounds stack access
    Date
    From: Arnd Bergmann <arnd@arndb.de>

    commit f051ae4f6c732c231046945b36234e977f8467c6 upstream.

    gcc -Warray-bounds warns about a serious bug in
    cyapa_pip_retrieve_data_structure:

    drivers/input/mouse/cyapa_gen6.c: In function 'cyapa_pip_retrieve_data_structure.constprop':
    include/linux/unaligned/access_ok.h:40:17: warning: array subscript -1 is outside array bounds of 'struct retrieve_data_struct_cmd[1]' [-Warray-bounds]
    40 | *((__le16 *)p) = cpu_to_le16(val);
    drivers/input/mouse/cyapa_gen6.c:569:13: note: while referencing 'cmd'
    569 | } __packed cmd;
    | ^~~

    Apparently the '-2' was added to the pointer instead of the value,
    writing garbage into the stack next to this variable.

    Fixes: c2c06c41f700 ("Input: cyapa - add gen6 device module support")
    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Link: https://lore.kernel.org/r/20201026161332.3708389-1-arnd@kernel.org
    Cc: stable@vger.kernel.org
    Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/input/mouse/cyapa_gen6.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/input/mouse/cyapa_gen6.c
    +++ b/drivers/input/mouse/cyapa_gen6.c
    @@ -573,7 +573,7 @@ static int cyapa_pip_retrieve_data_struc

    memset(&cmd, 0, sizeof(cmd));
    put_unaligned_le16(PIP_OUTPUT_REPORT_ADDR, &cmd.head.addr);
    - put_unaligned_le16(sizeof(cmd), &cmd.head.length - 2);
    + put_unaligned_le16(sizeof(cmd) - 2, &cmd.head.length);
    cmd.head.report_id = PIP_APP_CMD_REPORT_ID;
    cmd.head.cmd_code = PIP_RETRIEVE_DATA_STRUCTURE;
    put_unaligned_le16(read_offset, &cmd.read_offset);

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