drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform devicegrafted

platform_device_register_data() can fail and return an ERR_PTR, but the
return value is used without checking, leading to an invalid pointer
being stored in ddp_comp[].dev and passed to component_match_add() and
mtk_ddp_comp_init(), which could result in a kernel crash.

Add an IS_ERR() check to jump to the error handling path on failure.

Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Haojie Li <lihaojie@kylinos.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260825100845.438893-1-lihaojie@kylinos.cn/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/Documentation/security/digsig.rst b/Documentation/security/digsig.rst
new file mode 100644
index 000000000..de035f282
--- /dev/null
+++ b/Documentation/security/digsig.rst
@@ -0,0 +1,101 @@
+==================================
+Digital Signature Verification API
+==================================
+
+:Author: Dmitry Kasatkin
+:Date: 06.10.2011
+
+
+.. CONTENTS
+
+   1. Introduction
+   2. API
+   3. User-space utilities
+
+
+Introduction
+============
+
+Digital signature verification API provides a method to verify digital signature.
+Currently digital signatures are used by the IMA/EVM integrity protection subsystem.
+
+Digital signature verification is implemented using cut-down kernel port of
+GnuPG multi-precision integers (MPI) library. The kernel port provides
+memory allocation errors handling, has been refactored according to kernel
+coding style, and checkpatch.pl reported errors and warnings have been fixed.
+
+Public key and signature consist of header and MPIs::
+
+	struct pubkey_hdr {
+		uint8_t		version;	/* key format version */
+		time_t		timestamp;	/* key made, always 0 for now */
+		uint8_t		algo;
+		uint8_t		nmpi;
+		char		mpi[0];
+	} __packed;
+
+	struct signature_hdr {
+		uint8_t		version;	/* signature format version */
+		time_t		timestamp;	/* signature made */
+		uint8_t		algo;
+		uint8_t		hash;
+		uint8_t		keyid[8];
+		uint8_t		nmpi;
+		char		mpi[0];
+	} __packed;
+
+keyid equals to SHA1[12-19] over the total key content.
+Signature header is used as an input to generate a signature.
+Such approach insures that key or signature header could not be changed.
+It protects timestamp from been changed and can be used for rollback
+protection.
+
+API
+===
+
+API currently includes only 1 function::
+
+	digsig_verify() - digital signature verification with public key
+
+
+	/**
+	* digsig_verify() - digital signature verification with public key
+	* @keyring:	keyring to search key in
+	* @sig:	digital signature
+	* @sigen:	length of the signature
+	* @data:	data
+	* @datalen:	length of the data
+	* @return:	0 on success, -EINVAL otherwise
+	*
+	* Verifies data integrity against digital signature.
+	* Currently only RSA is supported.
+	* Normally hash of the content is used as a data for this function.
+	*
+	*/
+	int digsig_verify(struct key *keyring, const char *sig, int siglen,
+			  const char *data, int datalen);
+
+User-space utilities
+====================
+
+The signing and key management utilities evm-utils provide functionality
+to generate signatures, to load keys into the kernel keyring.
+Keys can be in PEM or converted to the kernel format.
+When the key is added to the kernel keyring, the keyid defines the name
+of the key: 5D2B05FC633EE3E8 in the example below.
+
+Here is example output of the keyctl utility::
+
+	$ keyctl show
+	Session Keyring
+	-3 --alswrv      0     0  keyring: _ses
+	603976250 --alswrv      0    -1   \_ keyring: _uid.0
+	817777377 --alswrv      0     0       \_ user: kmk
+	891974900 --alswrv      0     0       \_ encrypted: evm-key
+	170323636 --alswrv      0     0       \_ keyring: _module
+	548221616 --alswrv      0     0       \_ keyring: _ima
+	128198054 --alswrv      0     0       \_ keyring: _evm
+
+	$ keyctl list 128198054
+	1 key in keyring:
+	620789745: --alswrv     0     0 user: 5D2B05FC633EE3E8