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Commit 422b3db2 authored by Rishabh Bhatnagar's avatar Rishabh Bhatnagar Committed by Greg Kroah-Hartman
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firmware: Fix security issue with request_firmware_into_buf() 



When calling request_firmware_into_buf() with the FW_OPT_NOCACHE flag
it is expected that firmware is loaded into buffer from memory.
But inside alloc_lookup_fw_priv every new firmware that is loaded is
added to the firmware cache (fwc) list head. So if any driver requests
a firmware that is already loaded the code iterates over the above
mentioned list and it can end up giving a pointer to other device driver's
firmware buffer.
Also the existing copy may either be modified by drivers, remote processors
or even freed. This causes a potential security issue with batched requests
when using request_firmware_into_buf.

Fix alloc_lookup_fw_priv to not add to the fwc head list if FW_OPT_NOCACHE
is set, and also don't do the lookup in the list.

Fixes: 0e742e92 ("firmware: provide infrastructure to make fw caching optional")
[mcgrof: broken since feature introduction on v4.8]

Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: default avatarVikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: default avatarRishabh Bhatnagar <rishabhb@codeaurora.org>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6712cc9c

drivers/base/firmware_loader/main.c

+18 −12
Original line number Diff line number Diff line
@@ -209,11 +209,12 @@ static struct fw_priv *__lookup_fw_priv(const char *fw_name) 
static int alloc_lookup_fw_priv(const char *fw_name,

				struct firmware_cache *fwc,

				struct fw_priv **fw_priv, void *dbuf,

				size_t size)

				size_t size, enum fw_opt opt_flags)

{

	struct fw_priv *tmp;



	spin_lock(&fwc->lock);

	if (!(opt_flags & FW_OPT_NOCACHE)) {

		tmp = __lookup_fw_priv(fw_name);

		if (tmp) {

			kref_get(&tmp->ref);
@@ -222,8 +223,10 @@ static int alloc_lookup_fw_priv(const char *fw_name, 
			pr_debug("batched request - sharing the same struct fw_priv and lookup for multiple requests\n");

			return 1;

		}

	}



	tmp = __allocate_fw_priv(fw_name, fwc, dbuf, size);

	if (tmp)

	if (tmp && !(opt_flags & FW_OPT_NOCACHE))

		list_add(&tmp->list, &fwc->head);

	spin_unlock(&fwc->lock);
@@ -493,7 +496,8 @@ 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)

			  struct device *device, void *dbuf, size_t size,

			  enum fw_opt opt_flags)

{

	struct firmware *firmware;

	struct fw_priv *fw_priv;
@@ -511,7 +515,8 @@ _request_firmware_prepare(struct firmware **firmware_p, const char *name, 
		return 0; /* assigned */

	}



	ret = alloc_lookup_fw_priv(name, &fw_cache, &fw_priv, dbuf, size);

	ret = alloc_lookup_fw_priv(name, &fw_cache, &fw_priv, dbuf, size,

				  opt_flags);



	/*

	 * bind with 'priv' now to avoid warning in failure path
@@ -571,7 +576,8 @@ _request_firmware(const struct firmware **firmware_p, const char *name, 
		goto out;

	}



	ret = _request_firmware_prepare(&fw, name, device, buf, size);

	ret = _request_firmware_prepare(&fw, name, device, buf, size,

					opt_flags);

	if (ret <= 0) /* error or already assigned */

		goto out;