[PATCH net] net: iosm: Prevent underflow in ipc_chnl_cfg_get()

The bounds check on "index" doesn't catch negative values.  Using
ARRAY_SIZE() directly is more readable and more robust because it prevents
negative values for "index".  Fortunately we only pass valid values to
ipc_chnl_cfg_get() so this patch does not affect runtime.


Reported-by: Solomon Ucko <redacted>
Signed-off-by: Dan Carpenter <redacted>
---
I suspect this is bug report was based on static analysis.  I had a
Smatch check that used to print a warning, but then I modified it to
only complain when the index was user controlled.

 drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c b/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c
index 804e6c4f2c78..016c9c3aea8e 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c

@@ -64,10 +64,9 @@ static struct ipc_chnl_cfg modem_cfg[] = {
 
 int ipc_chnl_cfg_get(struct ipc_chnl_cfg *chnl_cfg, int index)
 {
-	int array_size = ARRAY_SIZE(modem_cfg);
-
-	if (index >= array_size) {
-		pr_err("index: %d and array_size %d", index, array_size);
+	if (index >= ARRAY_SIZE(modem_cfg)) {
+		pr_err("index: %d and array_size %lu", index,
+		       ARRAY_SIZE(modem_cfg));
 		return -ECHRNG;
 	}
 

-- 
2.20.1

Hi Dan,

array_size is removed so please change array_size in pr_err to array size (remove _).

Also change in pr_err array size format "%lu" is throwing warning [1] in 32bit env.

[1]
                 from ../drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c:6:
../drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c: In function 'ipc_chnl_cfg_get':
../include/linux/kern_levels.h:5:18: warning: format '%lu' expects argument of type
 'long unsigned int', but argument 3 has type 'unsigned int' [-Wformat=]

Regards,
Chetan

The bounds check on "index" doesn't catch negative values.  Using
ARRAY_SIZE() directly is more readable and more robust because it prevents
negative values for "index".  Fortunately we only pass valid values to
ipc_chnl_cfg_get() so this patch does not affect runtime.


Reported-by: Solomon Ucko <redacted>
Signed-off-by: Dan Carpenter <redacted>
---
v2: Remove underscore between "array" and "size".
    Use %zu print format specifier to fix a compile warning on 32 bit.

 drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c b/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c
index 804e6c4f2c78..016c9c3aea8e 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c

@@ -64,10 +64,9 @@ static struct ipc_chnl_cfg modem_cfg[] = {
 
 int ipc_chnl_cfg_get(struct ipc_chnl_cfg *chnl_cfg, int index)
 {
-	int array_size = ARRAY_SIZE(modem_cfg);
-
-	if (index >= array_size) {
-		pr_err("index: %d and array_size %d", index, array_size);
+	if (index >= ARRAY_SIZE(modem_cfg)) {
+		pr_err("index: %d and array size %zu", index,
+		       ARRAY_SIZE(modem_cfg));
 		return -ECHRNG;
 	}
 

-- 
2.20.1

-----Original Message-----
From: Dan Carpenter <redacted>
Sent: Monday, August 16, 2021 4:44 PM
To: Kumar, M Chetan <redacted>; Solomon Ucko
[off-list ref]
Cc: linuxwwan <redacted>; Loic Poulain
[off-list ref]; Sergey Ryazanov [off-list ref];
Johannes Berg [off-list ref]; David S. Miller
[off-list ref]; Jakub Kicinski [off-list ref];
netdev@vger.kernel.org; security@kernel.org
Subject: [PATCH v2 net] net: iosm: Prevent underflow in ipc_chnl_cfg_get()

The bounds check on "index" doesn't catch negative values.  Using
ARRAY_SIZE() directly is more readable and more robust because it prevents
negative values for "index".  Fortunately we only pass valid values to
ipc_chnl_cfg_get() so this patch does not affect runtime.


Reported-by: Solomon Ucko <redacted>
Signed-off-by: Dan Carpenter <redacted>
---
v2: Remove underscore between "array" and "size".
    Use %zu print format specifier to fix a compile warning on 32 bit.

 drivers/net/wwan/iosm/iosm_ipc_chnl_cfg.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Reviewed-by: M Chetan Kumar <redacted>

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Mon, 16 Aug 2021 14:13:33 +0300 you wrote:

The bounds check on "index" doesn't catch negative values.  Using
ARRAY_SIZE() directly is more readable and more robust because it prevents
negative values for "index".  Fortunately we only pass valid values to
ipc_chnl_cfg_get() so this patch does not affect runtime.


Reported-by: Solomon Ucko <redacted>
Signed-off-by: Dan Carpenter <redacted>

[...]

Here is the summary with links:
  - [v2,net] net: iosm: Prevent underflow in ipc_chnl_cfg_get()
    https://git.kernel.org/netdev/net/c/4f3f2e3fa043

You are awesome, thank you!
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