[PATCH 00/20] Manual replacement of all strlcpy in favor of strscpy

strlcpy() copy a C-String into a sized buffer, the result is always a
valid NULL-terminated that fits in the buffer, howerver it has severals
issues. It reads the source buffer first, which is dangerous if it is non
NULL-terminated or if the corresponding buffer is unbounded. Its safe
replacement is strscpy(), as suggested in the deprecated interface [1].

We plan to make this contribution in two steps:
- Firsly all cases of strlcpy's return value are manually replaced by the
  corresponding calls of strscpy() with the new handling of the return
  value (as the return code is different in case of error).
- Then all other cases are automatically replaced by using coccinelle.

This series covers manual replacements.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Romain Perier (20):
  cgroup: Manual replacement of the deprecated strlcpy() with return
    values
  crypto: Manual replacement of the deprecated strlcpy() with return
    values
  devlink: Manual replacement of the deprecated strlcpy() with return
    values
  dma-buf: Manual replacement of the deprecated strlcpy() with return
    values
  kobject: Manual replacement of the deprecated strlcpy() with return
    values
  ima: Manual replacement of the deprecated strlcpy() with return values
  SUNRPC: Manual replacement of the deprecated strlcpy() with return
    values
  kernfs: Manual replacement of the deprecated strlcpy() with return
    values
  m68k/atari: Manual replacement of the deprecated strlcpy() with return
    values
  module: Manual replacement of the deprecated strlcpy() with return
    values
  hwmon: Manual replacement of the deprecated strlcpy() with return
    values
  s390/hmcdrv: Manual replacement of the deprecated strlcpy() with
    return values
  scsi: zfcp: Manual replacement of the deprecated strlcpy() with return
    values
  target: Manual replacement of the deprecated strlcpy() with return
    values
  ALSA: usb-audio: Manual replacement of the deprecated strlcpy() with
    return values
  tracing/probe: Manual replacement of the deprecated strlcpy() with
    return values
  vt: Manual replacement of the deprecated strlcpy() with return values
  usb: gadget: f_midi: Manual replacement of the deprecated strlcpy()
    with return values
  usbip: usbip_host: Manual replacement of the deprecated strlcpy() with
    return values
  s390/watchdog: Manual replacement of the deprecated strlcpy() with
    return values

 arch/m68k/emu/natfeat.c                 |  6 +--
 crypto/lrw.c                            |  6 +--
 crypto/xts.c                            |  6 +--
 drivers/dma-buf/dma-buf.c               |  4 +-
 drivers/hwmon/pmbus/max20730.c          | 66 +++++++++++++------------
 drivers/s390/char/diag_ftp.c            |  4 +-
 drivers/s390/char/sclp_ftp.c            |  6 +--
 drivers/s390/scsi/zfcp_fc.c             |  8 +--
 drivers/target/target_core_configfs.c   | 33 ++++---------
 drivers/tty/vt/keyboard.c               |  5 +-
 drivers/usb/gadget/function/f_midi.c    |  4 +-
 drivers/usb/gadget/function/f_printer.c |  8 +--
 drivers/usb/usbip/stub_main.c           |  6 +--
 drivers/watchdog/diag288_wdt.c          | 12 +++--
 fs/kernfs/dir.c                         | 27 +++++-----
 kernel/cgroup/cgroup.c                  |  2 +-
 kernel/module.c                         |  4 +-
 kernel/trace/trace_uprobe.c             | 11 ++---
 lib/kobject_uevent.c                    |  6 +--
 net/core/devlink.c                      |  6 +--
 net/sunrpc/clnt.c                       |  6 ++-
 security/integrity/ima/ima_policy.c     |  8 ++-
 sound/usb/card.c                        |  4 +-
 23 files changed, 129 insertions(+), 119 deletions(-)

-- 
2.20.1

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>
---
 drivers/hwmon/pmbus/max20730.c |   66 +++++++++++++++++++++--------------------
 1 file changed, 35 insertions(+), 31 deletions(-)

diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
index 9dd3dd79bc18..a384b57b7327 100644
--- a/drivers/hwmon/pmbus/max20730.c
+++ b/drivers/hwmon/pmbus/max20730.c

@@ -107,7 +107,8 @@ struct max20730_debugfs_data {
 static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 				     size_t count, loff_t *ppos)
 {
-	int ret, len;
+	int ret;
+	ssize_t len;
 	int *idxp = file->private_data;
 	int idx = *idxp;
 	struct max20730_debugfs_data *psu = to_psu(idxp, idx);

@@ -148,13 +149,13 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET1_TSTAT_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "2000\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "2000\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "125\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "125\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "62.5\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "62.5\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "32\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "32\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_INTERNAL_GAIN:
 		val = (data->mfr_devset1 & MAX20730_MFR_DEVSET1_RGAIN_MASK)

@@ -163,35 +164,35 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 		if (data->id == max20734) {
 			/* AN6209 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.8\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "3.2\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.2\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "1.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.6\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "6.4\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "6.4\n", DEBUG_FS_DATA_MAX);
 		} else if (data->id == max20730 || data->id == max20710) {
 			/* AN6042 or AN6140 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "7.2\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "7.2\n", DEBUG_FS_DATA_MAX);
 		} else if (data->id == max20743) {
 			/* AN6042 */
 			if (val == 0)
-				len = strlcpy(tbuf, "0.45\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.45\n", DEBUG_FS_DATA_MAX);
 			else if (val == 1)
-				len = strlcpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "1.8\n", DEBUG_FS_DATA_MAX);
 			else if (val == 2)
-				len = strlcpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "0.9\n", DEBUG_FS_DATA_MAX);
 			else
-				len = strlcpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
+				len = strscpy(tbuf, "3.6\n", DEBUG_FS_DATA_MAX);
 		} else {
-			len = strlcpy(tbuf, "Not supported\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Not supported\n", DEBUG_FS_DATA_MAX);
 		}
 		break;
 	case MAX20730_DEBUGFS_BOOT_VOLTAGE:

@@ -199,26 +200,26 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET1_VBOOT_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "0.6484\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.6484\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "0.8984\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.8984\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "1.0\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1.0\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_OUT_V_RAMP_RATE:
 		val = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_VRATE)
 			>> MAX20730_MFR_DEVSET2_VRATE_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "4\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "4\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "2\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "2\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "1\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_OC_PROTECT_MODE:
 		ret = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_OCPM_MASK)

@@ -230,13 +231,13 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 			>> MAX20730_MFR_DEVSET2_SS_BIT_POS;
 
 		if (val == 0)
-			len = strlcpy(tbuf, "0.75\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "0.75\n", DEBUG_FS_DATA_MAX);
 		else if (val == 1)
-			len = strlcpy(tbuf, "1.5\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "1.5\n", DEBUG_FS_DATA_MAX);
 		else if (val == 2)
-			len = strlcpy(tbuf, "3\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "3\n", DEBUG_FS_DATA_MAX);
 		else
-			len = strlcpy(tbuf, "6\n", DEBUG_FS_DATA_MAX);
+			len = strscpy(tbuf, "6\n", DEBUG_FS_DATA_MAX);
 		break;
 	case MAX20730_DEBUGFS_IMAX:
 		ret = (data->mfr_devset2 & MAX20730_MFR_DEVSET2_IMAX_MASK)

@@ -287,9 +288,12 @@ static ssize_t max20730_debugfs_read(struct file *file, char __user *buf,
 				"%d.%d\n", ret / 10000, ret % 10000);
 		break;
 	default:
-		len = strlcpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
+		len = strscpy(tbuf, "Invalid\n", DEBUG_FS_DATA_MAX);
 	}
 
+	if (len == -E2BIG)
+		return -E2BIG;
+
 	return simple_read_from_buffer(buf, count, ppos, tbuf, len);
 }
 

On 2/22/21 7:12 AM, Romain Perier wrote:

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.

length

It can lead to linear read overflows, crashes, etc...

Not here. This description is misleading.

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>

This patch just adds pain to injury, as the source 'buffers' are all fixed
strings and their length will never exceed the maximum buffer length.
I really don't see the point of using strscpy() in this situation.

---
 drivers/hwmon/pmbus/max20730.c |   66 +++++++++++++++++++++--------------------

This patch only modifies a single driver and should be tagged as such.

On 2/22/21 8:12 AM, Romain Perier wrote:

strlcpy() copy a C-String into a sized buffer, the result is always a
valid NULL-terminated that fits in the buffer, howerver it has severals
issues. It reads the source buffer first, which is dangerous if it is non
NULL-terminated or if the corresponding buffer is unbounded. Its safe
replacement is strscpy(), as suggested in the deprecated interface [1].

We plan to make this contribution in two steps:
- Firsly all cases of strlcpy's return value are manually replaced by the
   corresponding calls of strscpy() with the new handling of the return
   value (as the return code is different in case of error).
- Then all other cases are automatically replaced by using coccinelle.

Cool. A quick check shows me 1031 strscpy() calls with no return
checks. All or some of these probably need to be reviewed and add
return checks. Is this something that is in the plan to address as
part of this work?

thanks,
-- Shuah

On Mon, 2021-02-22 at 07:46 -0800, Guenter Roeck wrote:

On 2/22/21 7:12 AM, Romain Perier wrote:

quoted

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.

length

quoted

It can lead to linear read overflows, crashes, etc...

Not here. This description is misleading.

quoted

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>

This patch just adds pain to injury, as the source 'buffers' are all fixed
strings and their length will never exceed the maximum buffer length.
I really don't see the point of using strscpy() in this situation.

Might as well just use strcpy (I'd still prefer stracpy)

https://lore.kernel.org/lkml/24bb53c57767c1c2a8f266c305a670f7@sk2.org/T/