2021-12-20 03:24:19

by Jason Wang

Subject: [PATCH] powerpc: use strscpy to copy strings

The strlcpy should not be used because it doesn't limit the source
length. So that it will lead some potential bugs.

But the strscpy doesn't require reading memory from the src string
beyond the specified "count" bytes, and since the return value is
easier to error-check than strlcpy()'s. In addition, the implementation
is robust to the string changing out from underneath it, unlike the
current strlcpy() implementation.

Thus, replace strlcpy with strscpy.

Signed-off-by: Jason Wang <[email protected]>
---
arch/powerpc/platforms/pasemi/misc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pasemi/misc.c b/arch/powerpc/platforms/pasemi/misc.c
index 1bf65d02d3ba..06a1ffd43bfe 100644
--- a/arch/powerpc/platforms/pasemi/misc.c
+++ b/arch/powerpc/platforms/pasemi/misc.c
@@ -35,7 +35,7 @@ static int __init find_i2c_driver(struct device_node *node,
for (i = 0; i < ARRAY_SIZE(i2c_devices); i++) {
if (!of_device_is_compatible(node, i2c_devices[i].of_device))
continue;
- if (strlcpy(info->type, i2c_devices[i].i2c_type,
+ if (strscpy(info->type, i2c_devices[i].i2c_type,
I2C_NAME_SIZE) >= I2C_NAME_SIZE)
return -ENOMEM;
return 0;
--
2.34.1

2021-12-20 10:23:21

by David Laight

Subject: RE: [PATCH] powerpc: use strscpy to copy strings

From: Jason Wang
> Sent: 20 December 2021 03:24
>
> The strlcpy should not be used because it doesn't limit the source
> length. So that it will lead some potential bugs.
>
> But the strscpy doesn't require reading memory from the src string
> beyond the specified "count" bytes, and since the return value is
> easier to error-check than strlcpy()'s. In addition, the implementation
> is robust to the string changing out from underneath it, unlike the
> current strlcpy() implementation.
>
> Thus, replace strlcpy with strscpy.
>
> Signed-off-by: Jason Wang <[email protected]>
> ---
> arch/powerpc/platforms/pasemi/misc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/pasemi/misc.c b/arch/powerpc/platforms/pasemi/misc.c
> index 1bf65d02d3ba..06a1ffd43bfe 100644
> --- a/arch/powerpc/platforms/pasemi/misc.c
> +++ b/arch/powerpc/platforms/pasemi/misc.c
> @@ -35,7 +35,7 @@ static int __init find_i2c_driver(struct device_node *node,
> for (i = 0; i < ARRAY_SIZE(i2c_devices); i++) {
> if (!of_device_is_compatible(node, i2c_devices[i].of_device))
> continue;
> - if (strlcpy(info->type, i2c_devices[i].i2c_type,
> + if (strscpy(info->type, i2c_devices[i].i2c_type,
> I2C_NAME_SIZE) >= I2C_NAME_SIZE)
> return -ENOMEM;

Isn't that the wrong overflow check?
Doesn't strscpy() return a -ve errno value on failure
(just to cause a different buffer overflow issue?)

Not that any kind of overflow is actually possible in that over-engineered
code fragment.

David

-
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