From: Jennifer Berringer jberring@redhat.com

When __nvmem_cell_entry_write() is called for an nvmem cell that does not need bit shifting, it requires that the len parameter exactly matches the nvmem cell size. However, when the nvmem cell has a nonzero bit_offset, it was skipping this check.

Accepting values of len larger than the cell size results in nvmem_cell_prepare_write_buffer() trying to write past the end of a heap buffer that it allocates. Add a check to avoid that problem and instead return -EINVAL when len doesn't match the number of bits expected by the nvmem cell when bit_offset is nonzero.

This check uses cell->nbits in order to allow providing the smaller size to cells that are shifted into another byte by bit_offset. For example, a cell with nbits=8 and nonzero bit_offset would have bytes=2 but should accept a 1-byte write here, although no current callers depend on this.

Fixes: 69aba7948cbe ("nvmem: Add a simple NVMEM framework for consumers") Cc: stable@vger.kernel.org Signed-off-by: Jennifer Berringer jberring@redhat.com Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org --- drivers/nvmem/core.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index d6494dfc20a7..845540b57e68 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -1790,6 +1790,8 @@ static int __nvmem_cell_entry_write(struct nvmem_cell_entry *cell, void *buf, si return -EINVAL;

if (cell->bit_offset || cell->nbits) { + if (len != BITS_TO_BYTES(cell->nbits) && len != cell->bytes) + return -EINVAL; buf = nvmem_cell_prepare_write_buffer(cell, buf, len); if (IS_ERR(buf)) return PTR_ERR(buf);