[PATCH] Input: hideep - fix the uninitialized use in hideep_nvm_unlock()

Inside function hideep_nvm_unlock(), variable "unmask_code" could
be uninitialized if hideep_pgm_r_reg() returns error, however, it
is used in the later if statement after an "and" operation, which
is potentially unsafe.

Signed-off-by: Yizhuo <redacted>
---
 drivers/input/touchscreen/hideep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/hideep.c

b/drivers/input/touchscreen/hideep.c
index ddad4a82a5e5..49b713ad4384 100644

--- a/drivers/input/touchscreen/hideep.c
+++ b/drivers/input/touchscreen/hideep.c

@@ -363,7 +363,7 @@ static int hideep_enter_pgm(struct hideep_ts *ts)

 static void hideep_nvm_unlock(struct hideep_ts *ts)
 {
-       u32 unmask_code;
+       u32 unmask_code = 0;

        hideep_pgm_w_reg(ts, HIDEEP_FLASH_CFG, HIDEEP_NVM_SFR_RPAGE);
        hideep_pgm_r_reg(ts, 0x0000000C, &unmask_code);

-- 
2.17.1

Hi Yizhuo,

On Tue, Jun 15, 2021 at 10:26:09AM -0700, Yizhuo Zhai wrote:

Inside function hideep_nvm_unlock(), variable "unmask_code" could
be uninitialized if hideep_pgm_r_reg() returns error, however, it
is used in the later if statement after an "and" operation, which
is potentially unsafe.

I do not think that simply initializing the variable makes the code
behave any better. If we want to fix this properly we need to check for
errors returned by hideep_pgm_r_reg() and hideep_pgm_w_reg() and exit
this function early, signalling the caller about errors.

Thanks.

-- 
Dmitry

Hi Demitry:

Thanks for your quick response, following your advice, a careful way
is changing the return type of  "hideep_nvm_unlock()" from void to
int, and its caller "hideep_program_nvm()" also needs to add the
return check.

If this sounds ok, I would go ahead to modify the patch accordingly.

On Tue, Jun 15, 2021 at 11:15 AM Dmitry Torokhov
[off-list ref] wrote:

Hi Yizhuo,

On Tue, Jun 15, 2021 at 10:26:09AM -0700, Yizhuo Zhai wrote:

quoted

Inside function hideep_nvm_unlock(), variable "unmask_code" could
be uninitialized if hideep_pgm_r_reg() returns error, however, it
is used in the later if statement after an "and" operation, which
is potentially unsafe.

I do not think that simply initializing the variable makes the code
behave any better. If we want to fix this properly we need to check for
errors returned by hideep_pgm_r_reg() and hideep_pgm_w_reg() and exit
this function early, signalling the caller about errors.

quoted

Signed-off-by: Yizhuo <redacted>
---
 drivers/input/touchscreen/hideep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/hideep.c

b/drivers/input/touchscreen/hideep.c
index ddad4a82a5e5..49b713ad4384 100644

--- a/drivers/input/touchscreen/hideep.c
+++ b/drivers/input/touchscreen/hideep.c

@@ -363,7 +363,7 @@ static int hideep_enter_pgm(struct hideep_ts *ts)

 static void hideep_nvm_unlock(struct hideep_ts *ts)
 {
-       u32 unmask_code;
+       u32 unmask_code = 0;

        hideep_pgm_w_reg(ts, HIDEEP_FLASH_CFG, HIDEEP_NVM_SFR_RPAGE);
        hideep_pgm_r_reg(ts, 0x0000000C, &unmask_code);
--

2.17.1

Thanks.

--
Dmitry

-- 
Kind Regards,

Yizhuo Zhai

Computer Science, Graduate Student
University of California, Riverside

On Tue, Jun 15, 2021 at 11:57:36AM -0700, Yizhuo Zhai wrote:

Hi Demitry:

Thanks for your quick response, following your advice, a careful way
is changing the return type of  "hideep_nvm_unlock()" from void to
int, and its caller "hideep_program_nvm()" also needs to add the
return check.

If this sounds ok, I would go ahead to modify the patch accordingly.

Yes, this sounds right.

On Tue, Jun 15, 2021 at 11:15 AM Dmitry Torokhov
[off-list ref] wrote:

quoted

Hi Yizhuo,

On Tue, Jun 15, 2021 at 10:26:09AM -0700, Yizhuo Zhai wrote:

quoted

Inside function hideep_nvm_unlock(), variable "unmask_code" could
be uninitialized if hideep_pgm_r_reg() returns error, however, it
is used in the later if statement after an "and" operation, which
is potentially unsafe.

I do not think that simply initializing the variable makes the code
behave any better. If we want to fix this properly we need to check for
errors returned by hideep_pgm_r_reg() and hideep_pgm_w_reg() and exit
this function early, signalling the caller about errors.

quoted

Signed-off-by: Yizhuo <redacted>
---
 drivers/input/touchscreen/hideep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/hideep.c

b/drivers/input/touchscreen/hideep.c
index ddad4a82a5e5..49b713ad4384 100644

--- a/drivers/input/touchscreen/hideep.c
+++ b/drivers/input/touchscreen/hideep.c

@@ -363,7 +363,7 @@ static int hideep_enter_pgm(struct hideep_ts *ts)

 static void hideep_nvm_unlock(struct hideep_ts *ts)
 {
-       u32 unmask_code;
+       u32 unmask_code = 0;

        hideep_pgm_w_reg(ts, HIDEEP_FLASH_CFG, HIDEEP_NVM_SFR_RPAGE);
        hideep_pgm_r_reg(ts, 0x0000000C, &unmask_code);
--

2.17.1

Thanks.

--
Dmitry

-- 
Kind Regards,

Yizhuo Zhai

Computer Science, Graduate Student
University of California, Riverside

-- 
Dmitry