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Miller" , Maxime Ripard , Chen-Yu Tsai , Eric Biggers , linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] crypto: sun4i-ss - reduce stack usage Message-ID: <20190618131234.GA8474@Red> References: <20190617132538.2759714-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190617132538.2759714-1-arnd@arndb.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Mon, Jun 17, 2019 at 03:25:17PM +0200, Arnd Bergmann wrote: > After the latest addition, the stack usage of sun4i_ss_cipher_poll > grew beyond the warning limit when KASAN is enabled: > > drivers/crypto/sunxi-ss/sun4i-ss-cipher.c:118:12: error: stack frame size of 1152 bytes in function 'sun4i_ss_cipher_poll' [-Werror,-Wframe-larger-than=] > static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > > Reduce it in three ways: > > - split out the new code into a separate function so its stack > usage can overlap that of the sun4i_ss_opti_poll() code path > - mark both special cases as noinline_for_stack, which should > ideally result in a tail call that frees the rest of the > stack > - move the buf and obuf variables into the code blocks in > which they are used. > > The three separate functions now use 144, 640 and 304 bytes of kernel > stack, respectively. > > Fixes: 0ae1f46c55f8 ("crypto: sun4i-ss - fallback when length is not multiple of blocksize") > Signed-off-by: Arnd Bergmann > --- > drivers/crypto/sunxi-ss/sun4i-ss-cipher.c | 47 +++++++++++++++-------- > 1 file changed, 30 insertions(+), 17 deletions(-) > > diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c b/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c > index 7b0c42882830..4ab14d58e85b 100644 > --- a/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c > +++ b/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c > @@ -12,7 +12,7 @@ > */ > #include "sun4i-ss.h" > > -static int sun4i_ss_opti_poll(struct skcipher_request *areq) > +static int noinline_for_stack sun4i_ss_opti_poll(struct skcipher_request *areq) > { > struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(areq); > struct sun4i_tfm_ctx *op = crypto_skcipher_ctx(tfm); > @@ -114,6 +114,29 @@ static int sun4i_ss_opti_poll(struct skcipher_request *areq) > return err; > } > > + > +static int noinline_for_stack sun4i_ss_cipher_poll_fallback(struct skcipher_request *areq) > +{ > + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(areq); > + struct sun4i_tfm_ctx *op = crypto_skcipher_ctx(tfm); > + struct sun4i_cipher_req_ctx *ctx = skcipher_request_ctx(areq); > + SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, op->fallback_tfm); > + int err; > + > + skcipher_request_set_sync_tfm(subreq, op->fallback_tfm); > + skcipher_request_set_callback(subreq, areq->base.flags, NULL, > + NULL); > + skcipher_request_set_crypt(subreq, areq->src, areq->dst, > + areq->cryptlen, areq->iv); > + if (ctx->mode & SS_DECRYPTION) > + err = crypto_skcipher_decrypt(subreq); > + else > + err = crypto_skcipher_encrypt(subreq); > + skcipher_request_zero(subreq); > + > + return err; > +} > + > /* Generic function that support SG with size not multiple of 4 */ > static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > { > @@ -140,8 +163,6 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > unsigned int todo; > struct sg_mapping_iter mi, mo; > unsigned int oi, oo; /* offset for in and out */ > - char buf[4 * SS_RX_MAX];/* buffer for linearize SG src */ > - char bufo[4 * SS_TX_MAX]; /* buffer for linearize SG dst */ > unsigned int ob = 0; /* offset in buf */ > unsigned int obo = 0; /* offset in bufo*/ > unsigned int obl = 0; /* length of data in bufo */ > @@ -178,20 +199,8 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > if (no_chunk == 1 && !need_fallback) > return sun4i_ss_opti_poll(areq); > > - if (need_fallback) { > - SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, op->fallback_tfm); > - skcipher_request_set_sync_tfm(subreq, op->fallback_tfm); > - skcipher_request_set_callback(subreq, areq->base.flags, NULL, > - NULL); > - skcipher_request_set_crypt(subreq, areq->src, areq->dst, > - areq->cryptlen, areq->iv); > - if (ctx->mode & SS_DECRYPTION) > - err = crypto_skcipher_decrypt(subreq); > - else > - err = crypto_skcipher_encrypt(subreq); > - skcipher_request_zero(subreq); > - return err; > - } > + if (need_fallback) > + return sun4i_ss_cipher_poll_fallback(areq); > > spin_lock_irqsave(&ss->slock, flags); > > @@ -224,6 +233,8 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > > while (oleft) { > if (ileft) { > + char buf[4 * SS_RX_MAX];/* buffer for linearize SG src */ > + > /* > * todo is the number of consecutive 4byte word that we > * can read from current SG > @@ -281,6 +292,8 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq) > oo = 0; > } > } else { > + char bufo[4 * SS_TX_MAX]; /* buffer for linearize SG dst */ > + > /* > * read obl bytes in bufo, we read at maximum for > * emptying the device > -- > 2.20.0 > Tested-by: Corentin LABBE