On Sat, Jan 12, 2019 at 7:28 AM Willy Tarreau <[email protected]> wrote: > > From: Silvio Cesare <[email protected]> > > Change snprintf to scnprintf. There are generally two cases where using > snprintf causes problems. > > 1) Uses of size += snprintf(buf, SIZE - size, fmt, ...) > In this case, if snprintf would have written more characters than what the > buffer size (SIZE) is, then size will end up larger than SIZE. In later > uses of snprintf, SIZE - size will result in a negative number, leading > to problems. Note that size might already be too large by using > size = snprintf before the code reaches a case of size += snprintf. > > 2) If size is ultimately used as a length parameter for a copy back to user > space, then it will potentially allow for a buffer overflow and information > disclosure when size is greater than SIZE. When the size is used to index > the buffer directly, we can have memory corruption. This also means when > size = snprintf... is used, it may also cause problems since size may become > large. Copying to userspace is mitigated by the HARDENED_USERCOPY kernel > configuration. > > The solution to these issues is to use scnprintf which returns the number of > characters actually written to the buffer, so the size variable will never > exceed SIZE. > > Signed-off-by: Silvio Cesare <[email protected]> > Cc: Pierre-Louis Bossart <[email protected]> > Cc: Liam Girdwood <[email protected]> > Cc: Jie Yang <[email protected]> > Cc: Dan Carpenter <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Will Deacon <[email protected]> > Cc: Greg KH <[email protected]> > Signed-off-by: Willy Tarreau <[email protected]>
This should get a Cc: stable, IMO. Reviewed-by: Kees Cook <[email protected]> -Kees > > --- > sound/soc/intel/skylake/skl-debug.c | 28 ++++++++++++++-------------- > 1 file changed, 14 insertions(+), 14 deletions(-) > > diff --git a/sound/soc/intel/skylake/skl-debug.c > b/sound/soc/intel/skylake/skl-debug.c > index 5d7ac2ee7a3c..bb28db734fb7 100644 > --- a/sound/soc/intel/skylake/skl-debug.c > +++ b/sound/soc/intel/skylake/skl-debug.c > @@ -43,7 +43,7 @@ static ssize_t skl_print_pins(struct skl_module_pin *m_pin, > char *buf, > ssize_t ret = 0; > > for (i = 0; i < max_pin; i++) > - ret += snprintf(buf + size, MOD_BUF - size, > + ret += scnprintf(buf + size, MOD_BUF - size, > "%s %d\n\tModule %d\n\tInstance %d\n\t" > "In-used %s\n\tType %s\n" > "\tState %d\n\tIndex %d\n", > @@ -59,7 +59,7 @@ static ssize_t skl_print_pins(struct skl_module_pin *m_pin, > char *buf, > static ssize_t skl_print_fmt(struct skl_module_fmt *fmt, char *buf, > ssize_t size, bool direction) > { > - return snprintf(buf + size, MOD_BUF - size, > + return scnprintf(buf + size, MOD_BUF - size, > "%s\n\tCh %d\n\tFreq %d\n\tBit depth %d\n\t" > "Valid bit depth %d\n\tCh config %#x\n\tInterleaving > %d\n\t" > "Sample Type %d\n\tCh Map %#x\n", > @@ -81,16 +81,16 @@ static ssize_t module_read(struct file *file, char __user > *user_buf, > if (!buf) > return -ENOMEM; > > - ret = snprintf(buf, MOD_BUF, "Module:\n\tUUID %pUL\n\tModule id %d\n" > + ret = scnprintf(buf, MOD_BUF, "Module:\n\tUUID %pUL\n\tModule id %d\n" > "\tInstance id %d\n\tPvt_id %d\n", mconfig->guid, > mconfig->id.module_id, mconfig->id.instance_id, > mconfig->id.pvt_id); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Resources:\n\tMCPS %#x\n\tIBS %#x\n\tOBS %#x\t\n", > mconfig->mcps, mconfig->ibs, mconfig->obs); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Module data:\n\tCore %d\n\tIn queue %d\n\t" > "Out queue %d\n\tType %s\n", > mconfig->core_id, mconfig->max_in_queue, > @@ -100,38 +100,38 @@ static ssize_t module_read(struct file *file, char > __user *user_buf, > ret += skl_print_fmt(mconfig->in_fmt, buf, ret, true); > ret += skl_print_fmt(mconfig->out_fmt, buf, ret, false); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Fixup:\n\tParams %#x\n\tConverter %#x\n", > mconfig->params_fixup, mconfig->converter); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Module Gateway:\n\tType %#x\n\tVbus %#x\n\tHW conn > %#x\n\tSlot %#x\n", > mconfig->dev_type, mconfig->vbus_id, > mconfig->hw_conn_type, mconfig->time_slot); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Pipeline:\n\tID %d\n\tPriority %d\n\tConn Type > %d\n\t" > "Pages %#x\n", mconfig->pipe->ppl_id, > mconfig->pipe->pipe_priority, > mconfig->pipe->conn_type, > mconfig->pipe->memory_pages); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "\tParams:\n\t\tHost DMA %d\n\t\tLink DMA %d\n", > mconfig->pipe->p_params->host_dma_id, > mconfig->pipe->p_params->link_dma_id); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "\tPCM params:\n\t\tCh %d\n\t\tFreq %d\n\t\tFormat > %d\n", > mconfig->pipe->p_params->ch, > mconfig->pipe->p_params->s_freq, > mconfig->pipe->p_params->s_fmt); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "\tLink %#x\n\tStream %#x\n", > mconfig->pipe->p_params->linktype, > mconfig->pipe->p_params->stream); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "\tState %d\n\tPassthru %s\n", > mconfig->pipe->state, > mconfig->pipe->passthru ? "true" : "false"); > @@ -141,7 +141,7 @@ static ssize_t module_read(struct file *file, char __user > *user_buf, > ret += skl_print_pins(mconfig->m_out_pin, buf, > mconfig->max_out_queue, ret, false); > > - ret += snprintf(buf + ret, MOD_BUF - ret, > + ret += scnprintf(buf + ret, MOD_BUF - ret, > "Other:\n\tDomain %d\n\tHomogeneous Input %s\n\t" > "Homogeneous Output %s\n\tIn Queue Mask %d\n\t" > "Out Queue Mask %d\n\tDMA ID %d\n\tMem Pages %d\n\t" > @@ -199,7 +199,7 @@ static ssize_t fw_softreg_read(struct file *file, char > __user *user_buf, > __iowrite32_copy(d->fw_read_buff, fw_reg_addr, w0_stat_sz >> > 2); > > for (offset = 0; offset < FW_REG_SIZE; offset += 16) { > - ret += snprintf(tmp + ret, FW_REG_BUF - ret, "%#.4x: ", > offset); > + ret += scnprintf(tmp + ret, FW_REG_BUF - ret, "%#.4x: ", > offset); > hex_dump_to_buffer(d->fw_read_buff + offset, 16, 16, 4, > tmp + ret, FW_REG_BUF - ret, 0); > ret += strlen(tmp + ret); > -- > 2.19.2 > -- Kees Cook
