linux-kernel - [PATCH 4.19 106/120] media: ngene: Fix out-of-bounds bug in ngene_command_config_free

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Message-Id: <20210726153835.846935839@linuxfoundation.org>
Date:   Mon, 26 Jul 2021 17:39:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: [PATCH 4.19 106/120] media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf()

From: Gustavo A. R. Silva <gustavoars@...nel.org>

commit 8d4abca95ecc82fc8c41912fa0085281f19cc29f upstream.

Fix an 11-year old bug in ngene_command_config_free_buf() while
addressing the following warnings caught with -Warray-bounds:

arch/alpha/include/asm/string.h:22:16: warning: '__builtin_memcpy' offset [12, 16] from the object at 'com' is out of the bounds of referenced subobject 'config' with type 'unsigned char' at offset 10 [-Warray-bounds]
arch/x86/include/asm/string_32.h:182:25: warning: '__builtin_memcpy' offset [12, 16] from the object at 'com' is out of the bounds of referenced subobject 'config' with type 'unsigned char' at offset 10 [-Warray-bounds]

The problem is that the original code is trying to copy 6 bytes of
data into a one-byte size member _config_ of the wrong structue
FW_CONFIGURE_BUFFERS, in a single call to memcpy(). This causes a
legitimate compiler warning because memcpy() overruns the length
of &com.cmd.ConfigureBuffers.config. It seems that the right
structure is FW_CONFIGURE_FREE_BUFFERS, instead, because it contains
6 more members apart from the header _hdr_. Also, the name of
the function ngene_command_config_free_buf() suggests that the actual
intention is to ConfigureFreeBuffers, instead of ConfigureBuffers
(which takes place in the function ngene_command_config_buf(), above).

Fix this by enclosing those 6 members of struct FW_CONFIGURE_FREE_BUFFERS
into new struct config, and use &com.cmd.ConfigureFreeBuffers.config as
the destination address, instead of &com.cmd.ConfigureBuffers.config,
when calling memcpy().

This also helps with the ongoing efforts to globally enable
-Warray-bounds and get us closer to being able to tighten the
FORTIFY_SOURCE routines on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Fixes: dae52d009fc9 ("V4L/DVB: ngene: Initial check-in")
Cc: stable@...r.kernel.org
Reported-by: kernel test robot <lkp@...el.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Link: https://lore.kernel.org/linux-hardening/20210420001631.GA45456@embeddedor/
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/media/pci/ngene/ngene-core.c |    2 +-
 drivers/media/pci/ngene/ngene.h      |   14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

--- a/drivers/media/pci/ngene/ngene-core.c
+++ b/drivers/media/pci/ngene/ngene-core.c
@@ -398,7 +398,7 @@ static int ngene_command_config_free_buf
 
 	com.cmd.hdr.Opcode = CMD_CONFIGURE_FREE_BUFFER;
 	com.cmd.hdr.Length = 6;
-	memcpy(&com.cmd.ConfigureBuffers.config, config, 6);
+	memcpy(&com.cmd.ConfigureFreeBuffers.config, config, 6);
 	com.in_len = 6;
 	com.out_len = 0;
 
--- a/drivers/media/pci/ngene/ngene.h
+++ b/drivers/media/pci/ngene/ngene.h
@@ -419,12 +419,14 @@ enum _BUFFER_CONFIGS {
 
 struct FW_CONFIGURE_FREE_BUFFERS {
 	struct FW_HEADER hdr;
-	u8   UVI1_BufferLength;
-	u8   UVI2_BufferLength;
-	u8   TVO_BufferLength;
-	u8   AUD1_BufferLength;
-	u8   AUD2_BufferLength;
-	u8   TVA_BufferLength;
+	struct {
+		u8   UVI1_BufferLength;
+		u8   UVI2_BufferLength;
+		u8   TVO_BufferLength;
+		u8   AUD1_BufferLength;
+		u8   AUD2_BufferLength;
+		u8   TVA_BufferLength;
+	} __packed config;
 } __attribute__ ((__packed__));
 
 struct FW_CONFIGURE_UART {