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 On 4/21/21 12:40, Kees Cook wrote: > On Mon, Apr 19, 2021 at 07:16:31PM -0500, Gustavo A. R. Silva wrote: >> 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: stable@xxxxxxxxxxxxxxx >> Reported-by: kernel test robot <lkp@xxxxxxxxx> >> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> > > 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 <keescook@xxxxxxxxxxxx> > > -Kees > >> --- >> drivers/media/pci/ngene/ngene-core.c | 2 +- >> drivers/media/pci/ngene/ngene.h | 14 ++++++++------ >> 2 files changed, 9 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/media/pci/ngene/ngene-core.c b/drivers/media/pci/ngene/ngene-core.c >> index 07f342db6701..7481f553f959 100644 >> --- a/drivers/media/pci/ngene/ngene-core.c >> +++ b/drivers/media/pci/ngene/ngene-core.c >> @@ -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; >> >> diff --git a/drivers/media/pci/ngene/ngene.h b/drivers/media/pci/ngene/ngene.h >> index 84f04e0e0cb9..3d296f1998a1 100644 >> --- a/drivers/media/pci/ngene/ngene.h >> +++ b/drivers/media/pci/ngene/ngene.h >> @@ -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 { >> -- >> 2.27.0 >> >
