[PATCH] nvmem: core: Fix possible buffer overflow on nvmem cell write

[Loic Poulain]

Nothing prevents a nvmem consumer to try writing excessive data to a
given nvmem cell (except when bit_offset is 0). The allocated buffer
of size 'cell->bytes' in nvmem_cell_prepare_write_buffer may not be
large enough to host the copied 'len' bytes.

Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxx>
---
 drivers/nvmem/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index eaf6a3fe8ca6..0b27ab3b3b86 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1654,6 +1654,9 @@ static void *nvmem_cell_prepare_write_buffer(struct nvmem_cell_entry *cell,
 	int i, rc, nbits, bit_offset = cell->bit_offset;
 	u8 v, *p, *buf, *b, pbyte, pbits;
 
+	if (len > cell->bytes)
+		return ERR_PTR(-EINVAL);
+
 	nbits = cell->nbits;
 	buf = kzalloc(cell->bytes, GFP_KERNEL);
 	if (!buf)
-- 
2.34.1