From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Date: Sat, 30 Jan 2016 14:44:32 +0000 Subject: [patch] video: fbdev: metronomefb: two harmless off by one bugs Message-Id: <20160130144432.GF3462@mwanda> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jean-Christophe Plagniol-Villard , Jaya Kumar Cc: Tomi Valkeinen , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org par->metromem_cmd->args[] is an array of 31 elements of size u16. Here we have initialized the first "i" elements and want to set the rest to zero. The issue here is that ARRAY_SIZE(par->metromem_cmd->args) is 31 and not 32 as in the original code. It means that we set ->csum to zero, but that is harmless because we immediately set it to the correct value on the next line. Still, the buffer overflow upsets static checkers so let's correct the math. Signed-off-by: Dan Carpenter diff --git a/drivers/video/fbdev/metronomefb.c b/drivers/video/fbdev/metronomefb.c index ad04a01..abb6bbf 100644 --- a/drivers/video/fbdev/metronomefb.c +++ b/drivers/video/fbdev/metronomefb.c @@ -354,7 +354,8 @@ static int metronome_powerup_cmd(struct metronomefb_par *par) } /* the rest are 0 */ - memset((u8 *) (par->metromem_cmd->args + i), 0, (32-i)*2); + memset(&par->metromem_cmd->args[i], 0, + (ARRAY_SIZE(par->metromem_cmd->args) - i) * 2); par->metromem_cmd->csum = cs; @@ -376,7 +377,8 @@ static int metronome_config_cmd(struct metronomefb_par *par) memcpy(par->metromem_cmd->args, epd_frame_table[par->dt].config, sizeof(epd_frame_table[par->dt].config)); /* the rest are 0 */ - memset((u8 *) (par->metromem_cmd->args + 4), 0, (32-4)*2); + memset(&par->metromem_cmd->args[4], 0, + (ARRAY_SIZE(par->metromem_cmd->args) - 4) * 2); par->metromem_cmd->csum = 0xCC10; par->metromem_cmd->csum += calc_img_cksum(par->metromem_cmd->args, 4);