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comedi: Fix initialization of data for instructions that write to subdevice
[ Upstream commit 46d8c744136ce2454aa4c35c138cc06817f92b8e ] Some Comedi subdevice instruction handlers are known to access instruction data elements beyond the first `insn->n` elements in some cases. The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions allocate at least `MIN_SAMPLES` (16) data elements to deal with this, but they do not initialize all of that. For Comedi instruction codes that write to the subdevice, the first `insn->n` data elements are copied from user-space, but the remaining elements are left uninitialized. That could be a problem if the subdevice instruction handler reads the uninitialized data. Ensure that the first `MIN_SAMPLES` elements are initialized before calling these instruction handlers, filling the uncopied elements with 0. For `do_insnlist_ioctl()`, the same data buffer elements are used for handling a list of instructions, so ensure the first `MIN_SAMPLES` elements are initialized for each instruction that writes to the subdevice. Fixes: ed9eccbe ("Staging: add comedi core") Cc: stable@vger.kernel.org # 5.13+ Signed-off-by:Ian Abbott <abbotti@mev.co.uk> Link: https://lore.kernel.org/r/20250707161439.88385-1-abbotti@mev.co.uk Signed-off-by: