Commit 8eceab19 authored Apr 02, 2026 by Douya Le Committed by Herbert Xu Apr 03, 2026

crypto: af_alg - limit RX SG extraction by receive buffer budget



Make af_alg_get_rsgl() limit each RX scatterlist extraction to the
remaining receive buffer budget.

af_alg_get_rsgl() currently uses af_alg_readable() only as a gate
before extracting data into the RX scatterlist. Limit each extraction
to the remaining af_alg_rcvbuf(sk) budget so that receive-side
accounting matches the amount of data attached to the request.

If skcipher cannot obtain enough RX space for at least one chunk while
more data remains to be processed, reject the recvmsg call instead of
rounding the request length down to zero.

Fixes: e870456d ("crypto: algif_skcipher - overhaul memory management")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Douya Le <ldy3087146292@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

parent e0249411

crypto/af_alg.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1229,6 +1229,8 @@ int af_alg_get_rsgl(struct sock sk, struct msghdr msg, int flags,

		seglen = min_t(size_t, (maxsize - len),
		msg_data_left(msg));
		/* Never pin more pages than the remaining RX accounting budget. */
		seglen = min_t(size_t, seglen, af_alg_rcvbuf(sk));

		if (list_empty(&areq->rsgl_list)) {
		rsgl = &areq->first_rsgl;

crypto/algif_skcipher.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -130,6 +130,11 @@ static int _skcipher_recvmsg(struct socket sock, struct msghdr msg,
		* full block size buffers.
		*/
		if (ctx->more \|\| len < ctx->used) {
		if (len < bs) {
		err = -EINVAL;
		goto free;
		}

		len -= len % bs;
		cflags \|= CRYPTO_SKCIPHER_REQ_NOTFINAL;
		}