On Thu, 12 Mar 2020 11:17:14 +0100,
Harald Freudenberger wrote:
>
> On 11.03.20 10:09, Takashi Iwai wrote:
> > Since snprintf() returns the would-be-output size instead of the
> > actual output size, the succeeding calls may go beyond the given
> > buffer limit. Fix it by replacing with scnprintf().
> >
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > ---
> > drivers/s390/crypto/zcrypt_cex4.c | 26 +++++++++++++-------------
> > 1 file changed, 13 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/zcrypt_cex4.c b/drivers/s390/crypto/zcrypt_cex4.c
> > index 9a9d02e19774..dea96d5b65fb 100644
> > --- a/drivers/s390/crypto/zcrypt_cex4.c
> > +++ b/drivers/s390/crypto/zcrypt_cex4.c
> > @@ -128,16 +128,16 @@ static ssize_t cca_mkvps_show(struct device *dev,
> > n = snprintf(buf, PAGE_SIZE, "AES NEW: - -\n");
> >
> > if (ci.cur_mk_state >= '1' && ci.cur_mk_state <= '2')
> > - n += snprintf(buf + n, PAGE_SIZE - n, "AES CUR: %s 0x%016llx\n",
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "AES CUR: %s 0x%016llx\n",
> > cao_state[ci.cur_mk_state - '1'], ci.cur_mkvp);
> > else
> > - n += snprintf(buf + n, PAGE_SIZE - n, "AES CUR: - -\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "AES CUR: - -\n");
> >
> > if (ci.old_mk_state >= '1' && ci.old_mk_state <= '2')
> > - n += snprintf(buf + n, PAGE_SIZE - n, "AES OLD: %s 0x%016llx\n",
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "AES OLD: %s 0x%016llx\n",
> > cao_state[ci.old_mk_state - '1'], ci.old_mkvp);
> > else
> > - n += snprintf(buf + n, PAGE_SIZE - n, "AES OLD: - -\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "AES OLD: - -\n");
> >
> > return n;
> > }
> > @@ -251,11 +251,11 @@ static ssize_t ep11_card_op_modes_show(struct device *dev,
> > if (ci.op_mode & (1 << ep11_op_modes[i].mode_bit)) {
> > if (n > 0)
> > buf[n++] = ' ';
> > - n += snprintf(buf + n, PAGE_SIZE - n,
> > + n += scnprintf(buf + n, PAGE_SIZE - n,
> > "%s", ep11_op_modes[i].mode_txt);
> > }
> > }
> > - n += snprintf(buf + n, PAGE_SIZE - n, "\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
> >
> > return n;
> > }
> > @@ -305,21 +305,21 @@ static ssize_t ep11_mkvps_show(struct device *dev,
> > cwk_state[di.cur_wk_state - '0']);
> > bin2hex(buf + n, di.cur_wkvp, sizeof(di.cur_wkvp));
> > n += 2 * sizeof(di.cur_wkvp);
> > - n += snprintf(buf + n, PAGE_SIZE - n, "\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
> > } else
> > n = snprintf(buf, PAGE_SIZE, "WK CUR: - -\n");
> >
> > if (di.new_wk_state == '0') {
> > - n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s -\n",
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s -\n",
> > nwk_state[di.new_wk_state - '0']);
> > } else if (di.new_wk_state >= '1' && di.new_wk_state <= '2') {
> > - n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s 0x",
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s 0x",
> > nwk_state[di.new_wk_state - '0']);
> > bin2hex(buf + n, di.new_wkvp, sizeof(di.new_wkvp));
> > n += 2 * sizeof(di.new_wkvp);
> > - n += snprintf(buf + n, PAGE_SIZE - n, "\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
> > } else
> > - n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: - -\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: - -\n");
> >
> > return n;
> > }
> > @@ -346,11 +346,11 @@ static ssize_t ep11_queue_op_modes_show(struct device *dev,
> > if (di.op_mode & (1 << ep11_op_modes[i].mode_bit)) {
> > if (n > 0)
> > buf[n++] = ' ';
> > - n += snprintf(buf + n, PAGE_SIZE - n,
> > + n += scnprintf(buf + n, PAGE_SIZE - n,
> > "%s", ep11_op_modes[i].mode_txt);
> > }
> > }
> > - n += snprintf(buf + n, PAGE_SIZE - n, "\n");
> > + n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
> >
> > return n;
> > }
>
> Thanks for this patch.
>
> I will use this as a trigger point to rework all the snprintfs within the ap bus and zcrypt code
> and replace them with scnprintf wherever the return code is used. Did not know that
> there are issues with snprintf ... This article gives some background: https://lwn.net/Articles/69419/
>
> The updates will go into the s390 subsystem and will be forwarded to the upstream kernel with the
> next kernel merge window.
Covering the whole snprintf() usage would be nicer, yes.
Thanks!
Takashi
