Messages in this thread | | | From | Guenter Roeck <> | Date | Tue, 14 Dec 2021 15:02:41 -0800 | Subject | Re: [PATCH] platform/chrome: cros_ec: fix read overflow in cros_ec_lpc_readmem() |
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On Thu, Dec 9, 2021 at 6:35 AM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > If bytes is larger than EC_MEMMAP_SIZE (255) then "EC_MEMMAP_SIZE - > bytes" is a very high unsigned value and basically offset is > accepted. The second problem is that it uses >= instead of > so this > means that we are not able to read the very last byte. > > Fixes: ec2f33ab582b ("platform/chrome: Add cros_ec_lpc driver for x86 devices") > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > drivers/platform/chrome/cros_ec_lpc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c > index d6306d2a096f..7e1d175def9f 100644 > --- a/drivers/platform/chrome/cros_ec_lpc.c > +++ b/drivers/platform/chrome/cros_ec_lpc.c > @@ -290,7 +290,8 @@ static int cros_ec_lpc_readmem(struct cros_ec_device *ec, unsigned int offset, > char *s = dest; > int cnt = 0; > > - if (offset >= EC_MEMMAP_SIZE - bytes) > + if (offset > EC_MEMMAP_SIZE || > + bytes > EC_MEMMAP_SIZE - offset)
I think that means we have the same problem if offset > EC_MEMMAP_SIZE, only now that condition isn't detected anymore because EC_MEMMAP_SIZE - offset is a very large number. I think what we really want is if (offset + bytes > EC_MEMMAP_SIZE) only without the overflow. Not sure how we can get there without checking each part. if (offset > EC_MEMMAP_SIZE || bytes > EC_MEMMAP_SIZE || bytes + offset > EC_MEMMAP_SIZE) return -EINVAL; Maybe that ? if ((u64) offset + bytes > EC_MEMMAP_SIZE) return -EINVAL;
Thanks, Guenter
> return -EINVAL; > > /* fixed length */ > -- > 2.20.1 >
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