Bug 1813491

Description of problem:
tcmu_cdb_print_info has a fixed size 193 bytes scratch buffer on the stack,
defined here:

void tcmu_cdb_print_info(struct tcmu_device *dev,
const struct tcmulib_cmd *cmd,
const char *info)
{
int i, n, bytes;
char fix[CDB_FIX_SIZE], *buf;

    buf = fix;
Further down, it uses sprintf to write some bytes in 2-digit hex format to
buf, with each byte occupying 3 bytes in buf:

    for (i = 0, n = 0; i < bytes; i++) {
            n += sprintf(buf + n, "%x ", cmd->cdb[i]);
    }
To avoid overflowing the stack buffer, there is a check earlier in the
function which performs a heap allocation if bytes is too large:

    if (bytes > CDB_FIX_SIZE) {
            buf = malloc(CDB_TO_BUF_SIZE(bytes));
            if (!buf) {
                    tcmu_dev_err(dev, "out of memory\n");
                    return;
            }
    }
But this check looks wrong. If bytes > 64, then the previously mentioned for
loop will overflow the 193 byte stack buffer. I think it should be:

    if (bytes > CDB_FIX_BYTES) {
Correcting this isn't sufficient on its own though, as this check doesn't
take in to account that an additional string (info) is written to buf and
can also result in the stack buffer overflowing:

    if (info)
            n += sprintf(buf + n, "%s", info);

Version-Release number of selected component (if applicable):


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