| Message ID | 20210607152348.GX1955@kadam (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] media: firewire: firedtv-avc: fix a buffer overflow in avc_ca_pmt() | expand |
On Mon 2021-06-07 18:23:48, Dan Carpenter wrote: > The bounds checking in avc_ca_pmt() is not strict enough. It should > be checking "read_pos + 4" because it's reading 5 bytes. If the > "es_info_length" is non-zero then it reads a 6th byte so there needs to > be an additional check for that. > > I also added checks for the "write_pos". I don't think these are > required because "read_pos" and "write_pos" are tied together so > checking one ought to be enough. But they make the code easier to > understand for me. The check on write_pos is: > > if (write_pos + 4 >= sizeof(c->operand) - 4) { > > The first "+ 4" is because we're writing 5 bytes and the last " - 4" > is to leave space for the CRC. > > The other problem is that "length" can be invalid. It comes from > "data_length" in fdtv_ca_pmt(). > > Cc: stable@vger.kernel.org > Reported-by: Luo Likang <luolikang@nsfocus.com> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> I do not see this fix in 5.14-rc1. Has it been solved another way in the end, please? Best Regards, Petr
diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c index 2bf9467b917d..71991f8638e6 100644 --- a/drivers/media/firewire/firedtv-avc.c +++ b/drivers/media/firewire/firedtv-avc.c @@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length) read_pos += program_info_length; write_pos += program_info_length; } - while (read_pos < length) { + while (read_pos + 4 < length) { + if (write_pos + 4 >= sizeof(c->operand) - 4) { + ret = -EINVAL; + goto out; + } c->operand[write_pos++] = msg[read_pos++]; c->operand[write_pos++] = msg[read_pos++]; c->operand[write_pos++] = msg[read_pos++]; @@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length) c->operand[write_pos++] = es_info_length >> 8; c->operand[write_pos++] = es_info_length & 0xff; if (es_info_length > 0) { + if (read_pos >= length) { + ret = -EINVAL; + goto out; + } pmt_cmd_id = msg[read_pos++]; if (pmt_cmd_id != 1 && pmt_cmd_id != 4) dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n", pmt_cmd_id); - if (es_info_length > sizeof(c->operand) - 4 - - write_pos) { + if (es_info_length > sizeof(c->operand) - 4 - write_pos || + es_info_length > length - read_pos) { ret = -EINVAL; goto out; } diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c index 9363d005e2b6..2d6992ac5dd6 100644 --- a/drivers/media/firewire/firedtv-ci.c +++ b/drivers/media/firewire/firedtv-ci.c @@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg) } else { data_length = msg->msg[3]; } + if (data_length > sizeof(msg->msg) - data_pos) + return -EINVAL; return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length); }
The bounds checking in avc_ca_pmt() is not strict enough. It should be checking "read_pos + 4" because it's reading 5 bytes. If the "es_info_length" is non-zero then it reads a 6th byte so there needs to be an additional check for that. I also added checks for the "write_pos". I don't think these are required because "read_pos" and "write_pos" are tied together so checking one ought to be enough. But they make the code easier to understand for me. The check on write_pos is: if (write_pos + 4 >= sizeof(c->operand) - 4) { The first "+ 4" is because we're writing 5 bytes and the last " - 4" is to leave space for the CRC. The other problem is that "length" can be invalid. It comes from "data_length" in fdtv_ca_pmt(). Cc: stable@vger.kernel.org Reported-by: Luo Likang <luolikang@nsfocus.com> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> --- v2: Change the limit in fdtv_ca_pmt() from "sizeof(msg->msg) - 4" to "sizeof(msg->msg) - data_pos". Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems very suspicous. Reading more than 4 bytes in the loop will lead to shift wrapping. drivers/media/firewire/firedtv-avc.c | 14 +++++++++++--- drivers/media/firewire/firedtv-ci.c | 2 ++ 2 files changed, 13 insertions(+), 3 deletions(-)