[PATCH 1/2] of: fdt: fix memory leak in fdt_ensure_space
Stefan Kerkmann
s.kerkmann at pengutronix.de
Thu Feb 1 00:34:24 PST 2024
Hello Ahmad,
On 31.01.24 18:15, Ahmad Fatoum wrote:
> Hello Stefan,
>
> On 31.01.24 17:56, Stefan Kerkmann wrote:
>> If the reallocation failed the old memory remains allocated and is never
>> freed, this is fixed by freeing the old memory on error.
>>
>> Signed-off-by: Stefan Kerkmann <s.kerkmann at pengutronix.de>
>> ---
>> drivers/of/fdt.c | 27 ++++++++++++++++++++-------
>> 1 file changed, 20 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 5c21bab5de..4f79a6120f 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -375,24 +375,37 @@ static void *memalign_realloc(void *orig, size_t oldsize, size_t newsize)
>>
>> static int fdt_ensure_space(struct fdt *fdt, int dtsize)
>> {
>> + size_t new_size;
>> + void *previous;
>> +
>> /*
>> * We assume strings and names have a maximum length of 1024
>> * whereas properties can be longer. We allocate new memory
>> * if we have less than 1024 bytes (+ the property size left.
>> */
>> if (fdt->str_size - fdt->str_nextofs < 1024) {
>> - fdt->strings = realloc(fdt->strings, fdt->str_size * 2);
>> - if (!fdt->strings)
>> + previous = fdt->strings;
>> + new_size = fdt->str_size * 2;
>> +
>> + if ((fdt->strings = realloc(previous, new_size)) == NULL) {
>
> IMO, it's less readable this way. I'd prefer we leave the realloc line and
> then !fdt->strings check on separate lines as before.
Applied.
>> + free(previous);
>
> This could happen later in the callers (look for out_free) if one wouldn't
> set fdt->strings to NULL on error. I don't feel strongly either way, so doing
> it this way is fine too.
>
Freeing the previous memory should happen in this function IMHO. In this
way `fdt->[strings|dt]` can be set to `NULL` and the caller will get a
segfaulty reminder if they choose to ignore error returned from the
function and still access `fdt->[strings|dt]`.
> Change looks good otherwise, so with first comment addressed:
>
Thank you :-).
> Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>
> Cheers,
> Ahmad
>
>> return -ENOMEM;
>> - fdt->str_size *= 2;
>> + }
>> +
>> + fdt->str_size = new_size;
>> }
>>
>> if (fdt->dt_size - fdt->dt_nextofs < 1024 + dtsize) {
>> - fdt->dt = memalign_realloc(fdt->dt, fdt->dt_size,
>> - fdt->dt_size * 2);
>> - if (!fdt->dt)
>> + previous = fdt->dt;
>> + new_size = fdt->dt_size * 2;
>> +
>> + if ((fdt->dt = memalign_realloc(previous, fdt->dt_size,
>> + new_size)) == NULL) {
>> + free(previous);
>> return -ENOMEM;
>> - fdt->dt_size *= 2;
>> + }
>> +
>> + fdt->dt_size = new_size;
>> }
>>
>> return 0;
>>
>
Cheers
Stefan
--
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