[PATCH v3] nvmem: core: fix possibly memleak when use nvmem_cell_info_to_nvmem_cell()

From: Vadym Kochan
Date: Wed Sep 23 2020 - 16:45:14 EST


Fix missing 'kfree_const(cell->name)' when call to
nvmem_cell_info_to_nvmem_cell() in several places:

* after nvmem_cell_info_to_nvmem_cell() failed during
nvmem_add_cells()

* during nvmem_device_cell_{read,write} when cell->name is
kstrdup'ed() without calling kfree_const() at the end, but
really there is no reason to do that 'dup, because the cell
instance is allocated on the stack for some short period to be
read/write without exposing it to the caller.

So the new nvmem_cell_info_to_nvmem_cell_nodup() helper is introduced
which is used to convert cell_info -> cell without name duplication as
a lighweight version of nvmem_cell_info_to_nvmem_cell().

Fixes: e2a5402ec7c6 ("nvmem: Add nvmem_device based consumer apis.")
Signed-off-by: Vadym Kochan <vadym.kochan@xxxxxxxxxxx>
---
v3:
* rename __nvmem_cell_info_to_nvmem_cell() -> nvmem_cell_info_to_nvmem_cell_nodup()

* rephrase commit description a bit

* get rid of wrong func line wrapping

v2:
* remove not needed 'kfree_const(cell->name)' after nvmem_cell_info_to_nvmem_cell()
failed.

drivers/nvmem/core.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 6cd3edb2eaf6..10cd935cf30e 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -361,16 +361,14 @@ static void nvmem_cell_add(struct nvmem_cell *cell)
blocking_notifier_call_chain(&nvmem_notifier, NVMEM_CELL_ADD, cell);
}

-static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
- const struct nvmem_cell_info *info,
- struct nvmem_cell *cell)
+static int nvmem_cell_info_to_nvmem_cell_nodup(struct nvmem_device *nvmem,
+ const struct nvmem_cell_info *info,
+ struct nvmem_cell *cell)
{
cell->nvmem = nvmem;
cell->offset = info->offset;
cell->bytes = info->bytes;
- cell->name = kstrdup_const(info->name, GFP_KERNEL);
- if (!cell->name)
- return -ENOMEM;
+ cell->name = info->name;

cell->bit_offset = info->bit_offset;
cell->nbits = info->nbits;
@@ -382,13 +380,30 @@ static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
dev_err(&nvmem->dev,
"cell %s unaligned to nvmem stride %d\n",
- cell->name, nvmem->stride);
+ cell->name ?: "<unknown>", nvmem->stride);
return -EINVAL;
}

return 0;
}

+static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
+ const struct nvmem_cell_info *info,
+ struct nvmem_cell *cell)
+{
+ int err;
+
+ err = nvmem_cell_info_to_nvmem_cell_nodup(nvmem, info, cell);
+ if (err)
+ return err;
+
+ cell->name = kstrdup_const(info->name, GFP_KERNEL);
+ if (!cell->name)
+ return -ENOMEM;
+
+ return 0;
+}
+
/**
* nvmem_add_cells() - Add cell information to an nvmem device
*
@@ -1460,7 +1475,7 @@ ssize_t nvmem_device_cell_read(struct nvmem_device *nvmem,
if (!nvmem)
return -EINVAL;

- rc = nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
+ rc = nvmem_cell_info_to_nvmem_cell_nodup(nvmem, info, &cell);
if (rc)
return rc;

@@ -1490,7 +1505,7 @@ int nvmem_device_cell_write(struct nvmem_device *nvmem,
if (!nvmem)
return -EINVAL;

- rc = nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
+ rc = nvmem_cell_info_to_nvmem_cell_nodup(nvmem, info, &cell);
if (rc)
return rc;

--
2.17.1