[PATCH 0/2] Fixing bug that would segmentation fault

[PATCH 0/2] Fixing bug that would segmentation fault

[Luiz Sampaio]

This series of patches consists of one patch fixing a simple coding style
issue and one patch fixing a bug that would cause segmentation fault.
Basically, there was a pointer that was being dereferenced without testing
if the pointer exists. This patch adds a protection, returning EFAULT in
case the pointer is NULL.

Luiz Sampaio (2):
  auxdisplay: charlcd: fixing coding style issue
  auxdisplay: charlcd: checking for pointer reference before
    dereferencing

 drivers/auxdisplay/charlcd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.33.1

[PATCH 1/2] auxdisplay: charlcd: fixing coding style issue

[Luiz Sampaio]

Removing 'int' from 'unsigned long int' declaration, which is unnecessary.

Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
---
 drivers/auxdisplay/charlcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 304accde365c..cca3b600c0ba 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -37,7 +37,7 @@ struct charlcd_priv {
 	bool must_clear;
 
 	/* contains the LCD config state */
-	unsigned long int flags;
+	unsigned long flags;
 
 	/* Current escape sequence and it's length or -1 if outside */
 	struct {
-- 
2.33.1

[PATCH 2/2] auxdisplay: charlcd: checking for pointer reference before dereferencing

[Luiz Sampaio]

Check if the pointer lcd->ops->init_display exists before dereferencing it.
If a driver called charlcd_init() without defining the ops, this would
return segmentation fault, as happened to me when implementing a charlcd
driver.  Checking the pointer before dereferencing protects from
segmentation fault.

Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
---
 drivers/auxdisplay/charlcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index cca3b600c0ba..47363fb2fe94 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -578,6 +578,9 @@ static int charlcd_init(struct charlcd *lcd)
 	 * Since charlcd_init_display() needs to write data, we have to
 	 * enable mark the LCD initialized just before.
 	 */
+	if (!lcd->ops->init_display)
+		return -EFAULT;
+
 	ret = lcd->ops->init_display(lcd);
 	if (ret)
 		return ret;
-- 
2.33.1

Re: [PATCH 2/2] auxdisplay: charlcd: checking for pointer reference before dereferencing

[Miguel Ojeda]

On Sun, Nov 7, 2021 at 4:03 PM Luiz Sampaio <sampaio.ime@gmail.com> wrote:
>
> Check if the pointer lcd->ops->init_display exists before dereferencing it.
> If a driver called charlcd_init() without defining the ops, this would
> return segmentation fault, as happened to me when implementing a charlcd
> driver.  Checking the pointer before dereferencing protects from
> segmentation fault.

It can't hurt -- thanks! I think `EINVAL` makes more sense here, also
we could use `WARN_ON`:

    if (WARN_ON(!lcd->ops->init_display))
        return -EINVAL;

Cheers,
Miguel

Re: [PATCH 1/2] auxdisplay: charlcd: fixing coding style issue

[Miguel Ojeda]

On Sun, Nov 7, 2021 at 4:03 PM Luiz Sampaio <sampaio.ime@gmail.com> wrote:
>
> Removing 'int' from 'unsigned long int' declaration, which is unnecessary.

Not sure if this is a rule, but it is good to be consistent with the
rest of auxdisplay. Thanks!

Cheers,
Miguel

[PATCH v2 0/2] Fixing bug that would segmentation fault

[Luiz Sampaio]

This series of patches consists of one patch fixing a simple coding style
issue and one patch fixing a bug that would cause segmentation fault.
Basically, there was a pointer that was being dereferenced without testing
if the pointer exists. This patch adds a protection, returning EFAULT in
case the pointer is NULL.

Changes in v2:
- Changed return to -EINVAL and using WARN_ON as suggested 
- Note in response for Miguel's comment: for the first patch, I ran the
  script './scripts/checkpatch.pl --file --terse' to see with the file
had any coding style issue. That was when I was suggested to remove
'int' from 'unsigned long' declaration

Luiz Sampaio (2):
  auxdisplay: charlcd: fixing coding style issue
  auxdisplay: charlcd: checking for pointer reference before
    dereferencing

 drivers/auxdisplay/charlcd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.33.1

[PATCH v2 1/2] auxdisplay: charlcd: fixing coding style issue

[Luiz Sampaio]

Removing 'int' from 'unsigned long int' declaration, which is unnecessary.

Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
---
 drivers/auxdisplay/charlcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 304accde365c..cca3b600c0ba 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -37,7 +37,7 @@ struct charlcd_priv {
 	bool must_clear;
 
 	/* contains the LCD config state */
-	unsigned long int flags;
+	unsigned long flags;
 
 	/* Current escape sequence and it's length or -1 if outside */
 	struct {
-- 
2.33.1

[PATCH v2 2/2] auxdisplay: charlcd: checking for pointer reference before dereferencing

[Luiz Sampaio]

Check if the pointer lcd->ops->init_display exists before dereferencing it.
If a driver called charlcd_init() without defining the ops, this would
return segmentation fault, as happened to me when implementing a charlcd
driver.  Checking the pointer before dereferencing protects from
segmentation fault.

Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
---
 drivers/auxdisplay/charlcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index cca3b600c0ba..6d309e4971b6 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -578,6 +578,9 @@ static int charlcd_init(struct charlcd *lcd)
 	 * Since charlcd_init_display() needs to write data, we have to
 	 * enable mark the LCD initialized just before.
 	 */
+	if (WARN_ON(!lcd->ops->init_display))
+		return -EINVAL;
+
 	ret = lcd->ops->init_display(lcd);
 	if (ret)
 		return ret;
-- 
2.33.1

Re: [PATCH v2 2/2] auxdisplay: charlcd: checking for pointer reference before dereferencing

[Miguel Ojeda]

On Tue, Nov 9, 2021 at 11:07 PM Luiz Sampaio <sampaio.ime@gmail.com> wrote:
>
> Check if the pointer lcd->ops->init_display exists before dereferencing it.
> If a driver called charlcd_init() without defining the ops, this would
> return segmentation fault, as happened to me when implementing a charlcd
> driver.  Checking the pointer before dereferencing protects from
> segmentation fault.
>
> Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>

Queued up, thanks!

Cheers,
Miguel

Re: [PATCH v2 1/2] auxdisplay: charlcd: fixing coding style issue

[Miguel Ojeda]

On Tue, Nov 9, 2021 at 11:07 PM Luiz Sampaio <sampaio.ime@gmail.com> wrote:
>
> Removing 'int' from 'unsigned long int' declaration, which is unnecessary.
>
> Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>

Queued up, thanks!

Cheers,
Miguel