2022-09-01 15:47:56

by Dan Carpenter

Subject: [PATCH] crypto: cavium - prevent integer overflow loading firmware

The "ntohl(ucode->code_length) * 2" multiplication can have an
integer overflow.

Fixes: 9e2c7d99941d ("crypto: cavium - Add Support for Octeon-tx CPT Engine")
Signed-off-by: Dan Carpenter <[email protected]>
---
drivers/crypto/cavium/cpt/cptpf_main.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/cavium/cpt/cptpf_main.c b/drivers/crypto/cavium/cpt/cptpf_main.c
index 8c32d0eb8fcf..b196579dcd98 100644
--- a/drivers/crypto/cavium/cpt/cptpf_main.c
+++ b/drivers/crypto/cavium/cpt/cptpf_main.c
@@ -253,6 +253,7 @@ static int cpt_ucode_load_fw(struct cpt_device *cpt, const u8 *fw, bool is_ae)
const struct firmware *fw_entry;
struct device *dev = &cpt->pdev->dev;
struct ucode_header *ucode;
+ unsigned int code_length;
struct microcode *mcode;
int j, ret = 0;

@@ -263,7 +264,13 @@ static int cpt_ucode_load_fw(struct cpt_device *cpt, const u8 *fw, bool is_ae)
ucode = (struct ucode_header *)fw_entry->data;
mcode = &cpt->mcode[cpt->next_mc_idx];
memcpy(mcode->version, (u8 *)fw_entry->data, CPT_UCODE_VERSION_SZ);
- mcode->code_size = ntohl(ucode->code_length) * 2;
+
+ code_length = ntohl(ucode->code_length);
+ if (code_length >= INT_MAX / 2) {
+ ret = -EINVAL;
+ goto fw_release;
+ }
+ mcode->code_size = code_length;
if (!mcode->code_size) {
ret = -EINVAL;
goto fw_release;
--
2.35.1

2022-09-08 09:56:44

by Herbert Xu

Subject: Re: [PATCH] crypto: cavium - prevent integer overflow loading firmware

On Thu, Sep 01, 2022 at 06:32:53PM +0300, Dan Carpenter wrote:
>
> @@ -263,7 +264,13 @@ static int cpt_ucode_load_fw(struct cpt_device *cpt, const u8 *fw, bool is_ae)
> ucode = (struct ucode_header *)fw_entry->data;
> mcode = &cpt->mcode[cpt->next_mc_idx];
> memcpy(mcode->version, (u8 *)fw_entry->data, CPT_UCODE_VERSION_SZ);
> - mcode->code_size = ntohl(ucode->code_length) * 2;
> +
> + code_length = ntohl(ucode->code_length);
> + if (code_length >= INT_MAX / 2) {
> + ret = -EINVAL;
> + goto fw_release;
> + }
> + mcode->code_size = code_length;

Where did the "* 2" go?

BTW, what is the threat model here? If the firmware metadata can't
be trusted, shouldn't we be capping the firmware size at a level
a lot lower than INT_MAX?

Cheers,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

2022-09-15 13:52:09

by Dan Carpenter

Subject: Re: [PATCH] crypto: cavium - prevent integer overflow loading firmware

On Thu, Sep 08, 2022 at 05:42:54PM +0800, Herbert Xu wrote:
> On Thu, Sep 01, 2022 at 06:32:53PM +0300, Dan Carpenter wrote:
> >
> > @@ -263,7 +264,13 @@ static int cpt_ucode_load_fw(struct cpt_device *cpt, const u8 *fw, bool is_ae)
> > ucode = (struct ucode_header *)fw_entry->data;
> > mcode = &cpt->mcode[cpt->next_mc_idx];
> > memcpy(mcode->version, (u8 *)fw_entry->data, CPT_UCODE_VERSION_SZ);
> > - mcode->code_size = ntohl(ucode->code_length) * 2;
> > +
> > + code_length = ntohl(ucode->code_length);
> > + if (code_length >= INT_MAX / 2) {
> > + ret = -EINVAL;
> > + goto fw_release;
> > + }
> > + mcode->code_size = code_length;
>
> Where did the "* 2" go?

Crud. :/ Sorry.

>
> BTW, what is the threat model here? If the firmware metadata can't
> be trusted, shouldn't we be capping the firmware size at a level
> a lot lower than INT_MAX?

This is not firmware metadata, I'm fairly sure the fw_entry->data is raw
data from the file system. Realistically, if you can't trust your
firmware then you are probably toasted but there is a move to trust as
little as possible. Also Smatch marks data from the file system as
untrusted so it will generate static checker warnings.

regards,
dan carpenter