Hello Abdelrahman,
Thanks for your patch.
On 12.11.24 20:10, Abdelrahman Youssef wrote:
> While fuzzing, the name marked by FDT_BEGIN_NODE sometimes extends beyond
> the struct block area, Causing a heap-overflow.
>
> Since `maxlen` is an unsigned integer representing the length of name,
> It can be negative, So it overflows to large numbers, Causing strnlen()
> to overflow.
>
> So we can just change the type of maxlen to signed and check if it's negative.
>
> Signed-off-by: Abdelrahman Youssef <abdelrahmanyossef12@xxxxxxxxx>
> ---
Changelog would've been nice. This also should have been v3 not v2.
> drivers/of/fdt.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 2c3ea31394..d8d8a4922c 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -176,7 +176,7 @@ static struct device_node *__of_unflatten_dtb(const void *infdt, int size,
> void *dt_strings;
> struct fdt_header f;
> int ret;
> - unsigned int maxlen;
> + int maxlen;
> const struct fdt_header *fdt = infdt;
>
> ret = fdt_parse_header(infdt, size, &f);
> @@ -210,6 +210,11 @@ static struct device_node *__of_unflatten_dtb(const void *infdt, int size,
> maxlen = (unsigned long)fdt + f.off_dt_struct +
> f.size_dt_struct - (unsigned long)name;
>
> + if (maxlen < 0) {
> + ret = -ESPIPE;
> + goto err;
> + }
> +
> len = strnlen(name, maxlen + 1);
Hmm is this + 1 correct? I am wondering if we should be dropping
the + 1 here and make it maxlen <= 0 above.
What do you think?
Cheers,
Ahmad
> if (len > maxlen) {> ret = -ESPIPE;
--
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