media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf()

PATCH In review Gustavo A. R. Silva 3 participants 3 messages Apr 20, 2021 – Jul 20, 2021 Media (V4L/DVB)

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Gustavo A. R. Silva

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2021-04-20 00:16 UTC #0 lore raw

PATCH 1/1 media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf()

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 configuration 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 [email protected]

Reported-by kernel test robot <[email protected]>

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 drivers/media/pci/ngene/ngene-core.c |  2 +-
 drivers/media/pci/ngene/ngene.h      | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

drivers/media/pci/ngene/ngene-core.c +1 -1

index 07f342db6701..7481f553f959 100644
@@ -385,7 +385,7 @@ static int ngene_command_config_free_buf(struct ngene *dev, u8 *config)
 
 	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;

drivers/media/pci/ngene/ngene.h +8 -6

index 84f04e0e0cb9..3d296f1998a1 100644
@@ -407,12 +407,14 @@ 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 {

Signature · 1 line

2.27.0

Kees Cook

Reviewed-by on v1 1/1

2021-04-21 17:40 UTC #1 lore raw

Quoted 27 lines · Gustavo A. R. Silva

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 configuration 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().

Quoted 5 lines

Link https://github.com/KSPP/linux/issues/109
Fixes dae52d009fc9 ("V4L/DVB: ngene: Initial check-in")
Cc [email protected]
Reported-by kernel test robot <[email protected]>
Signed-off-by Gustavo A. R. Silva <[email protected]>

Nice find! Yeah, this looks like a copy/paste bug but it went unnoticed because it's occupying the same memory via the union. Heh.

Reviewed-by Kees Cook <[email protected]>

-Kees

Quoted 46 lines

---
 drivers/media/pci/ngene/ngene-core.c |  2 +-
 drivers/media/pci/ngene/ngene.h      | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

drivers/media/pci/ngene/ngene-core.c +1 -1

index 07f342db6701..7481f553f959 100644
@@ -385,7 +385,7 @@ static int ngene_command_config_free_buf(struct ngene *dev, u8 *config)
 
 	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;

drivers/media/pci/ngene/ngene.h +8 -6

index 84f04e0e0cb9..3d296f1998a1 100644
@@ -407,12 +407,14 @@ 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 {

Signature · 1 line

2.27.0

Signature · 1 line

Kees Cook

Gustavo A. R. Silva

2021-07-20 00:53 UTC #2 lore raw

Hi all,

I'm taking this in my tree[1] for 5.14-rc3.

Thanks
--
Gustavo

[1] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/log/?h=for-next/array-bounds

Quoted 88 lines · Kees Cook

Quoted 27 lines · Gustavo A. R. Silva
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 configuration 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().
Quoted 5 lines
Link https://github.com/KSPP/linux/issues/109
Fixes dae52d009fc9 ("V4L/DVB: ngene: Initial check-in")
Cc [email protected]
Reported-by kernel test robot <[email protected]>
Signed-off-by Gustavo A. R. Silva <[email protected]>
Nice find! Yeah, this looks like a copy/paste bug but it went unnoticed because it's occupying the same memory via the union. Heh.
Reviewed-by Kees Cook <[email protected]>
-Kees
Quoted 46 lines
---
 drivers/media/pci/ngene/ngene-core.c |  2 +-
 drivers/media/pci/ngene/ngene.h      | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)
drivers/media/pci/ngene/ngene-core.c +1 -1
index 07f342db6701..7481f553f959 100644
@@ -385,7 +385,7 @@ static int ngene_command_config_free_buf(struct ngene *dev, u8 *config)
 
 	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;
 
drivers/media/pci/ngene/ngene.h +8 -6
index 84f04e0e0cb9..3d296f1998a1 100644
@@ -407,12 +407,14 @@ 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 {
Signature · 1 line
2.27.0