2015-12-12 05:04:02

by Andrew Zaborowski

Subject: [PATCH] crypto: rsa-padding - don't allocate buffer on stack

Avoid the s390 compile "warning: 'pkcs1pad_encrypt_sign_complete'
uses dynamic stack allocation" reported by kbuild test robot. Don't
use a flat zero-filled buffer, instead zero the contents of the SGL.

Signed-off-by: Andrew Zaborowski <[email protected]>
---
crypto/rsa-pkcs1pad.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index accc67d..50f5c97 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -110,21 +110,32 @@ static int pkcs1pad_encrypt_sign_complete(struct akcipher_request *req, int err)
struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
struct pkcs1pad_ctx *ctx = akcipher_tfm_ctx(tfm);
struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
- uint8_t zeros[ctx->key_size - req_ctx->child_req.dst_len];
+ size_t pad_len = ctx->key_size - req_ctx->child_req.dst_len;
+ size_t chunk_len, pad_left;
+ struct sg_mapping_iter miter;

if (!err) {
- if (req_ctx->child_req.dst_len < ctx->key_size) {
- memset(zeros, 0, sizeof(zeros));
- sg_copy_from_buffer(req->dst,
- sg_nents_for_len(req->dst,
- sizeof(zeros)),
- zeros, sizeof(zeros));
+ if (pad_len) {
+ sg_miter_start(&miter, req->dst,
+ sg_nents_for_len(req->dst, pad_len),
+ SG_MITER_ATOMIC | SG_MITER_TO_SG);
+
+ pad_left = pad_len;
+ while (pad_left) {
+ sg_miter_next(&miter);
+
+ chunk_len = min(miter.length, pad_left);
+ memset(miter.addr, 0, chunk_len);
+ pad_left -= chunk_len;
+ }
+
+ sg_miter_stop(&miter);
}

sg_pcopy_from_buffer(req->dst,
sg_nents_for_len(req->dst, ctx->key_size),
req_ctx->out_buf, req_ctx->child_req.dst_len,
- sizeof(zeros));
+ pad_len);
}
req->dst_len = ctx->key_size;

--
2.1.4

2015-12-22 13:21:45

by Herbert Xu

Subject: Re: [PATCH] crypto: rsa-padding - don't allocate buffer on stack

Andrew Zaborowski <[email protected]> wrote:
> Avoid the s390 compile "warning: 'pkcs1pad_encrypt_sign_complete'
> uses dynamic stack allocation" reported by kbuild test robot. Don't
> use a flat zero-filled buffer, instead zero the contents of the SGL.
>
> Signed-off-by: Andrew Zaborowski <[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