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Subject[PATCH v2] memory: brcmstb_dpfe: fix array index out of bounds
Date
We would overrun the error_text array if we hit a TIMEOUT condition,
because we were using the error code "ETIMEDOUT" (which is 110) as an
array index.

We fix the problem by correcting the array index and by providing a
function to retrieve error messages rather than accessing the array
directly. The function includes a bounds check that prevents the array
from being overrun.

This patch was prepared in response to
https://lkml.org/lkml/2020/8/18/505.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
---

Changes since v1:
- Added link of the coverity report to the commit message.
- Added Florian's ack.
- Removed second "const" from get_error_text() return type
(thanks to the kernel test robot).

drivers/memory/brcmstb_dpfe.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/memory/brcmstb_dpfe.c b/drivers/memory/brcmstb_dpfe.c
index e08528b12cbd..dcf50bb8dd69 100644
--- a/drivers/memory/brcmstb_dpfe.c
+++ b/drivers/memory/brcmstb_dpfe.c
@@ -188,11 +188,6 @@ struct brcmstb_dpfe_priv {
struct mutex lock;
};

-static const char * const error_text[] = {
- "Success", "Header code incorrect", "Unknown command or argument",
- "Incorrect checksum", "Malformed command", "Timed out",
-};
-
/*
* Forward declaration of our sysfs attribute functions, so we can declare the
* attribute data structures early.
@@ -307,6 +302,20 @@ static const struct dpfe_api dpfe_api_v3 = {
},
};

+static const char *get_error_text(unsigned int i)
+{
+ static const char * const error_text[] = {
+ "Success", "Header code incorrect",
+ "Unknown command or argument", "Incorrect checksum",
+ "Malformed command", "Timed out", "Unknown error",
+ };
+
+ if (unlikely(i >= ARRAY_SIZE(error_text)))
+ i = ARRAY_SIZE(error_text) - 1;
+
+ return error_text[i];
+}
+
static bool is_dcpu_enabled(struct brcmstb_dpfe_priv *priv)
{
u32 val;
@@ -445,7 +454,7 @@ static int __send_command(struct brcmstb_dpfe_priv *priv, unsigned int cmd,
}
if (resp != 0) {
mutex_unlock(&priv->lock);
- return -ETIMEDOUT;
+ return -ffs(DCPU_RET_ERR_TIMEDOUT);
}

/* Compute checksum over the message */
@@ -695,7 +704,7 @@ static ssize_t generic_show(unsigned int command, u32 response[],

ret = __send_command(priv, command, response);
if (ret < 0)
- return sprintf(buf, "ERROR: %s\n", error_text[-ret]);
+ return sprintf(buf, "ERROR: %s\n", get_error_text(-ret));

return 0;
}
--
2.17.1
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