[PATCH v5 15/16] firmware: Add request_partial_firmware_into_buf()

From: Kees Cook
Date: Fri Oct 02 2020 - 13:39:06 EST

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From: Scott Branden <scott.branden@xxxxxxxxxxxx>

Add request_partial_firmware_into_buf() to allow for portions of a
firmware file to be read into a buffer. This is needed when large firmware
must be loaded in portions from a file on memory constrained systems.

Signed-off-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
Co-developed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
drivers/base/firmware_loader/firmware.h | 4 +
drivers/base/firmware_loader/main.c | 101 +++++++++++++++++++-----
include/linux/firmware.h | 12 +++
3 files changed, 99 insertions(+), 18 deletions(-)

diff --git a/drivers/base/firmware_loader/firmware.h b/drivers/base/firmware_loader/firmware.h
index f86de5d7e0d7..63bd29fdcb9c 100644
--- a/drivers/base/firmware_loader/firmware.h
+++ b/drivers/base/firmware_loader/firmware.h
@@ -32,6 +32,8 @@
* @FW_OPT_FALLBACK_PLATFORM: Enable fallback to device fw copy embedded in
* the platform's main firmware. If both this fallback and the sysfs
* fallback are enabled, then this fallback will be tried first.
+ * @FW_OPT_PARTIAL: Allow partial read of firmware instead of needing to read
+ * entire file.
*/
enum fw_opt {
FW_OPT_UEVENT = BIT(0),
@@ -41,6 +43,7 @@ enum fw_opt {
FW_OPT_NOCACHE = BIT(4),
FW_OPT_NOFALLBACK_SYSFS = BIT(5),
FW_OPT_FALLBACK_PLATFORM = BIT(6),
+ FW_OPT_PARTIAL = BIT(7),
};

enum fw_status {
@@ -68,6 +71,7 @@ struct fw_priv {
void *data;
size_t size;
size_t allocated_size;
+ size_t offset;
u32 opt_flags;
#ifdef CONFIG_FW_LOADER_PAGED_BUF
bool is_paged_buf;
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 78c8e44c08cb..78355095e00d 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -170,10 +170,19 @@ static struct fw_priv *__allocate_fw_priv(const char *fw_name,
struct firmware_cache *fwc,
void *dbuf,
size_t size,
+ size_t offset,
u32 opt_flags)
{
struct fw_priv *fw_priv;

+ /* For a partial read, the buffer must be preallocated. */
+ if ((opt_flags & FW_OPT_PARTIAL) && !dbuf)
+ return NULL;
+
+ /* Only partial reads are allowed to use an offset. */
+ if (offset != 0 && !(opt_flags & FW_OPT_PARTIAL))
+ return NULL;
+
fw_priv = kzalloc(sizeof(*fw_priv), GFP_ATOMIC);
if (!fw_priv)
return NULL;
@@ -188,6 +197,7 @@ static struct fw_priv *__allocate_fw_priv(const char *fw_name,
fw_priv->fwc = fwc;
fw_priv->data = dbuf;
fw_priv->allocated_size = size;
+ fw_priv->offset = offset;
fw_priv->opt_flags = opt_flags;
fw_state_init(fw_priv);
#ifdef CONFIG_FW_LOADER_USER_HELPER
@@ -216,12 +226,17 @@ static int alloc_lookup_fw_priv(const char *fw_name,
struct fw_priv **fw_priv,
void *dbuf,
size_t size,
+ size_t offset,
u32 opt_flags)
{
struct fw_priv *tmp;

spin_lock(&fwc->lock);
- if (!(opt_flags & FW_OPT_NOCACHE)) {
+ /*
+ * Do not merge requests that are marked to be non-cached or
+ * are performing partial reads.
+ */
+ if (!(opt_flags & (FW_OPT_NOCACHE | FW_OPT_PARTIAL))) {
tmp = __lookup_fw_priv(fw_name);
if (tmp) {
kref_get(&tmp->ref);
@@ -232,7 +247,7 @@ static int alloc_lookup_fw_priv(const char *fw_name,
}
}

- tmp = __allocate_fw_priv(fw_name, fwc, dbuf, size, opt_flags);
+ tmp = __allocate_fw_priv(fw_name, fwc, dbuf, size, offset, opt_flags);
if (tmp) {
INIT_LIST_HEAD(&tmp->list);
if (!(opt_flags & FW_OPT_NOCACHE))
@@ -490,6 +505,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
return -ENOMEM;

for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
+ size_t file_size = 0;
+ size_t *file_size_ptr = NULL;
+
/* skip the unset customized path */
if (!fw_path[i][0])
continue;
@@ -503,9 +521,18 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,

fw_priv->size = 0;

+ /*
+ * The total file size is only examined when doing a partial
+ * read; the "full read" case needs to fail if the whole
+ * firmware was not completely loaded.
+ */
+ if ((fw_priv->opt_flags & FW_OPT_PARTIAL) && buffer)
+ file_size_ptr = &file_size;
+
/* load firmware files from the mount namespace of init */
- rc = kernel_read_file_from_path_initns(path, 0, &buffer, msize,
- NULL,
+ rc = kernel_read_file_from_path_initns(path, fw_priv->offset,
+ &buffer, msize,
+ file_size_ptr,
READING_FIRMWARE);
if (rc < 0) {
if (rc != -ENOENT)
@@ -696,7 +723,7 @@ int assign_fw(struct firmware *fw, struct device *device)
static int
_request_firmware_prepare(struct firmware **firmware_p, const char *name,
struct device *device, void *dbuf, size_t size,
- u32 opt_flags)
+ size_t offset, u32 opt_flags)
{
struct firmware *firmware;
struct fw_priv *fw_priv;
@@ -715,7 +742,7 @@ _request_firmware_prepare(struct firmware **firmware_p, const char *name,
}

ret = alloc_lookup_fw_priv(name, &fw_cache, &fw_priv, dbuf, size,
- opt_flags);
+ offset, opt_flags);

/*
* bind with 'priv' now to avoid warning in failure path
@@ -762,9 +789,10 @@ static void fw_abort_batch_reqs(struct firmware *fw)
static int
_request_firmware(const struct firmware **firmware_p, const char *name,
struct device *device, void *buf, size_t size,
- u32 opt_flags)
+ size_t offset, u32 opt_flags)
{
struct firmware *fw = NULL;
+ bool nondirect = false;
int ret;

if (!firmware_p)
@@ -776,18 +804,22 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
}

ret = _request_firmware_prepare(&fw, name, device, buf, size,
- opt_flags);
+ offset, opt_flags);
if (ret <= 0) /* error or already assigned */
goto out;

ret = fw_get_filesystem_firmware(device, fw->priv, "", NULL);
+
+ /* Only full reads can support decompression, platform, and sysfs. */
+ if (!(opt_flags & FW_OPT_PARTIAL))
+ nondirect = true;
+
#ifdef CONFIG_FW_LOADER_COMPRESS
- if (ret == -ENOENT)
+ if (ret == -ENOENT && nondirect)
ret = fw_get_filesystem_firmware(device, fw->priv, ".xz",
fw_decompress_xz);
#endif
-
- if (ret == -ENOENT)
+ if (ret == -ENOENT && nondirect)
ret = firmware_fallback_platform(fw->priv);

if (ret) {
@@ -795,7 +827,9 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
dev_warn(device,
"Direct firmware load for %s failed with error %d\n",
name, ret);
- ret = firmware_fallback_sysfs(fw, name, device, opt_flags, ret);
+ if (nondirect)
+ ret = firmware_fallback_sysfs(fw, name, device,
+ opt_flags, ret);
} else
ret = assign_fw(fw, device);

@@ -838,7 +872,7 @@ request_firmware(const struct firmware **firmware_p, const char *name,

/* Need to pin this module until return */
__module_get(THIS_MODULE);
- ret = _request_firmware(firmware_p, name, device, NULL, 0,
+ ret = _request_firmware(firmware_p, name, device, NULL, 0, 0,
FW_OPT_UEVENT);
module_put(THIS_MODULE);
return ret;
@@ -865,7 +899,7 @@ int firmware_request_nowarn(const struct firmware **firmware, const char *name,

/* Need to pin this module until return */
__module_get(THIS_MODULE);
- ret = _request_firmware(firmware, name, device, NULL, 0,
+ ret = _request_firmware(firmware, name, device, NULL, 0, 0,
FW_OPT_UEVENT | FW_OPT_NO_WARN);
module_put(THIS_MODULE);
return ret;
@@ -889,7 +923,7 @@ int request_firmware_direct(const struct firmware **firmware_p,
int ret;

__module_get(THIS_MODULE);
- ret = _request_firmware(firmware_p, name, device, NULL, 0,
+ ret = _request_firmware(firmware_p, name, device, NULL, 0, 0,
FW_OPT_UEVENT | FW_OPT_NO_WARN |
FW_OPT_NOFALLBACK_SYSFS);
module_put(THIS_MODULE);
@@ -914,7 +948,7 @@ int firmware_request_platform(const struct firmware **firmware,

/* Need to pin this module until return */
__module_get(THIS_MODULE);
- ret = _request_firmware(firmware, name, device, NULL, 0,
+ ret = _request_firmware(firmware, name, device, NULL, 0, 0,
FW_OPT_UEVENT | FW_OPT_FALLBACK_PLATFORM);
module_put(THIS_MODULE);
return ret;
@@ -970,13 +1004,44 @@ request_firmware_into_buf(const struct firmware **firmware_p, const char *name,
return -EOPNOTSUPP;

__module_get(THIS_MODULE);
- ret = _request_firmware(firmware_p, name, device, buf, size,
+ ret = _request_firmware(firmware_p, name, device, buf, size, 0,
FW_OPT_UEVENT | FW_OPT_NOCACHE);
module_put(THIS_MODULE);
return ret;
}
EXPORT_SYMBOL(request_firmware_into_buf);

+/**
+ * request_partial_firmware_into_buf() - load partial firmware into a previously allocated buffer
+ * @firmware_p: pointer to firmware image
+ * @name: name of firmware file
+ * @device: device for which firmware is being loaded and DMA region allocated
+ * @buf: address of buffer to load firmware into
+ * @size: size of buffer
+ * @offset: offset into file to read
+ *
+ * This function works pretty much like request_firmware_into_buf except
+ * it allows a partial read of the file.
+ */
+int
+request_partial_firmware_into_buf(const struct firmware **firmware_p,
+ const char *name, struct device *device,
+ void *buf, size_t size, size_t offset)
+{
+ int ret;
+
+ if (fw_cache_is_setup(device, name))
+ return -EOPNOTSUPP;
+
+ __module_get(THIS_MODULE);
+ ret = _request_firmware(firmware_p, name, device, buf, size, offset,
+ FW_OPT_UEVENT | FW_OPT_NOCACHE |
+ FW_OPT_PARTIAL);
+ module_put(THIS_MODULE);
+ return ret;
+}
+EXPORT_SYMBOL(request_partial_firmware_into_buf);
+
/**
* release_firmware() - release the resource associated with a firmware image
* @fw: firmware resource to release
@@ -1009,7 +1074,7 @@ static void request_firmware_work_func(struct work_struct *work)

fw_work = container_of(work, struct firmware_work, work);

- _request_firmware(&fw, fw_work->name, fw_work->device, NULL, 0,
+ _request_firmware(&fw, fw_work->name, fw_work->device, NULL, 0, 0,
fw_work->opt_flags);
fw_work->cont(fw, fw_work->context);
put_device(fw_work->device); /* taken in request_firmware_nowait() */
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index cb3e2c06ed8a..c15acadc6cf4 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -53,6 +53,9 @@ int request_firmware_direct(const struct firmware **fw, const char *name,
struct device *device);
int request_firmware_into_buf(const struct firmware **firmware_p,
const char *name, struct device *device, void *buf, size_t size);
+int request_partial_firmware_into_buf(const struct firmware **firmware_p,
+ const char *name, struct device *device,
+ void *buf, size_t size, size_t offset);

void release_firmware(const struct firmware *fw);
#else
@@ -102,6 +105,15 @@ static inline int request_firmware_into_buf(const struct firmware **firmware_p,
return -EINVAL;
}

+static inline int request_partial_firmware_into_buf
+ (const struct firmware **firmware_p,
+ const char *name,
+ struct device *device,
+ void *buf, size_t size, size_t offset)
+{
+ return -EINVAL;
+}
+
#endif

int firmware_request_cache(struct device *device, const char *name);
--
2.25.1

Next message: Kees Cook: "[PATCH v5 10/16] module: Call security_kernel_post_load_data()"
Previous message: Kees Cook: "[PATCH v5 14/16] firmware: Store opt_flags in fw_priv"
In reply to: Kees Cook: "[PATCH v5 14/16] firmware: Store opt_flags in fw_priv"
Next in thread: Kees Cook: "[PATCH v5 10/16] module: Call security_kernel_post_load_data()"
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