On Thu, Dec 14, 2017 at 5:01 PM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> On Thu, Dec 14, 2017 at 1:31 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
>> The commit f6f828513290 ("pstore: pass allocated memory region back to
>> caller") changed the check of the return value from erst_read() in
>> erst_reader() in the following way:
>>
>> if (len == -ENOENT)
>> goto skip;
>> - else if (len < 0) {
>> - rc = -1;
>> + else if (len < sizeof(*rcd)) {
>> + rc = -EIO;
>> goto out;
>>
>> This introduced another bug: since the comparison with sizeof() is
>> cast to unsigned, a negative len value doesn't hit any longer.
>> As a result, when an error is returned from erst_read(), the code
>> falls through, and it may eventually lead to some weird thing like
>> memory corruption.
>>
>> This patch adds the negative error value check more explicitly for
>> addressing the issue.
Ew, nice catch, thanks!
>>
>> Fixes: f6f828513290 ("pstore: pass allocated memory region back to caller")
>
> That's ancient. :-)
>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> Tested-by: Jerry Tang <jtang@xxxxxxxx>
>> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
>> ---
>> drivers/acpi/apei/erst.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
>> index 6742f6c68034..9bff853e85f3 100644
>> --- a/drivers/acpi/apei/erst.c
>> +++ b/drivers/acpi/apei/erst.c
>> @@ -1007,7 +1007,7 @@ static ssize_t erst_reader(struct pstore_record *record)
>> /* The record may be cleared by others, try read next record */
>> if (len == -ENOENT)
>> goto skip;
>> - else if (len < sizeof(*rcd)) {
>> + else if (len < 0 || len < sizeof(*rcd)) {
>> rc = -EIO;
>> goto out;
>> }
>> --
>
> OK, I'm going to queue this up unless I see objections from Boris or Tony.
Please do, yes.
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
--
Kees Cook
Pixel Security
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