2016-09-28 14:38:42

by Jan Stancek

Subject: [PATCH] crypto: testmgr - add guard to dst buffer for ahash_export

Add a guard to 'state' buffer and warn if its consistency after
call to crypto_ahash_export() changes, so that any write that
goes beyond advertised statesize (and thus causing potential
memory corruption [1]) is more visible.

[1] https://marc.info/?l=linux-crypto-vger&m=147467656516085

Signed-off-by: Jan Stancek <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Marcelo Cerri <[email protected]>
---
crypto/testmgr.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index 5c9d5a5e7b65..96343bcae01e 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -209,16 +209,19 @@ static int ahash_partial_update(struct ahash_request **preq,
char *state;
struct ahash_request *req;
int statesize, ret = -EINVAL;
+ const char guard[] = { 0x00, 0xba, 0xad, 0x00 };

req = *preq;
statesize = crypto_ahash_statesize(
crypto_ahash_reqtfm(req));
- state = kmalloc(statesize, GFP_KERNEL);
+ state = kmalloc(statesize + sizeof(guard), GFP_KERNEL);
if (!state) {
pr_err("alt: hash: Failed to alloc state for %s\n", algo);
goto out_nostate;
}
+ memcpy(state + statesize, guard, sizeof(guard));
ret = crypto_ahash_export(req, state);
+ WARN_ON(memcmp(state + statesize, guard, sizeof(guard)));
if (ret) {
pr_err("alt: hash: Failed to export() for %s\n", algo);
goto out;
--
1.8.3.1

2016-10-02 14:37:18

by Herbert Xu

Subject: Re: [PATCH] crypto: testmgr - add guard to dst buffer for ahash_export

On Wed, Sep 28, 2016 at 04:38:37PM +0200, Jan Stancek wrote:
> Add a guard to 'state' buffer and warn if its consistency after
> call to crypto_ahash_export() changes, so that any write that
> goes beyond advertised statesize (and thus causing potential
> memory corruption [1]) is more visible.
>
> [1] https://marc.info/?l=linux-crypto-vger&m=147467656516085
>
> Signed-off-by: Jan Stancek <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: Marcelo Cerri <[email protected]>

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