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When running "i2c md 0 0 80000100", the function do_i2c_md parses the length into an unsigned int variable named length. The value is then moved to a signed variable: int nbytes = length; #define DISP_LINE_LEN 16 int linebytes = (nbytes > DISP_LINE_LEN) ? DISP_LINE_LEN : nbytes; ret = dm_i2c_read(dev, addr, linebuf, linebytes); On systems where integers are 32 bits wide, 0x80000100 is a negative value to "nbytes > DISP_LINE_LEN" is false and linebytes gets assigned 0x80000100 instead of 16. The consequence is that the function which reads from the i2c device (dm_i2c_read or i2c_read) is called with a 16-byte stack buffer to fill but with a size parameter which is too large. In some cases, this could trigger a crash. But with some i2c drivers, such as drivers/i2c/nx_i2c.c (used with "nexell,s5pxx18-i2c" bus), the size is actually truncated to a 16-bit integer. This is because function i2c_transfer expects an unsigned short length. In such a case, an attacker who can control the response of an i2c device can overwrite the return address of a function and execute arbitrary code through Return-Oriented Programming. Fix this issue by using unsigned integers types in do_i2c_md. While at it, make also alen unsigned, as signed sizes can cause vulnerabilities when people forgot to check that they can be negative. Signed-off-by: Nicolas Iooss <nicolas.iooss+uboot@ledger.fr> Reviewed-by: Heiko Schocher <hs@denx.de>
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