• Gustavo A. R. Silva's avatar
    media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf() · 8d4abca9
    Gustavo A. R. Silva authored
    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: dae52d00 ("V4L/DVB: ngene: Initial check-in")
    Cc: stable@vger.kernel.org
    Reported-by: default avatarkernel test robot <lkp@intel.com>
    Reviewed-by: default avatarKees Cook <keescook@chromium.org>
    Signed-off-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
    Link: https://lore.kernel.org/linux-hardening/20210420001631.GA45456@embeddedor/
    8d4abca9
ngene-core.c 43.1 KB