crypto: algif_aead - Revert to operating out-of-place

jira VULN-181881
cve CVE-2026-31431
commit-author Herbert Xu <herbert@gondor.apana.org.au>
commit a664bf3
upstream-diff |
	This kernel lacks upstream commits c1abe6f ("crypto: af_alg:
	Use extract_iter_to_sg() to create scatterlists") and f2804d0
	("crypto: algif_aead - use memcpy_sglist() instead of null
	skcipher"). As a result, there are two conflicts: the scatterlist
	table is located in a different member of `struct af_alg_sgl` and
	the null skcipher is used for copying between scatterlists instead
	of memcpy_sglist() (which is a helper that doesn't exist in this
	kernel version).

	The scatterlist table discrepancy is resolved by using the correct
	member of `struct af_alg_sgl`.

	The upstream patch's usage of memcpy_sglist() is replaced by a call
	to the null skcipher to perform the scatterlist copy instead.

This mostly reverts commit 72548b0 except for the copying of
the associated data.

There is no benefit in operating in-place in algif_aead since the
source and destination come from different mappings.  Get rid of
all the complexity added for in-place operation and just copy the
AD directly.

Fixes: 72548b0 ("crypto: algif_aead - copy AAD from src to dst")
	Reported-by: Taeyang Lee <0wn@theori.io>
	Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
(cherry picked from commit a664bf3)
	Signed-off-by: Sultan Alsawaf <sultan@ciq.com>

Author: kerneltoast

crypto/af_alg.c

@@ -525,15 +525,13 @@ static int af_alg_alloc_tsgl(struct sock *sk)
 /**
  * af_alg_count_tsgl - Count number of TX SG entries
  *
- * The counting starts from the beginning of the SGL to @bytes. If
- * an @offset is provided, the counting of the SG entries starts at the @offset.
+ * The counting starts from the beginning of the SGL to @bytes.
  *
  * @sk: socket of connection to user space
  * @bytes: Count the number of SG entries holding given number of bytes.
- * @offset: Start the counting of SG entries from the given offset.
  * Return: Number of TX SG entries found given the constraints
  */
-unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes, size_t offset)
+unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes)
 {
 	const struct alg_sock *ask = alg_sk(sk);
 	const struct af_alg_ctx *ctx = ask->private;
@@ -548,25 +546,11 @@ unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes, size_t offset)
 		const struct scatterlist *sg = sgl->sg;
 
 		for (i = 0; i < sgl->cur; i++) {
-			size_t bytes_count;
-
-			/* Skip offset */
-			if (offset >= sg[i].length) {
-				offset -= sg[i].length;
-				bytes -= sg[i].length;
-				continue;
-			}
-
-			bytes_count = sg[i].length - offset;
-
-			offset = 0;
 			sgl_count++;
-
-			/* If we have seen requested number of bytes, stop */
-			if (bytes_count >= bytes)
+			if (sg[i].length >= bytes)
 				return sgl_count;
 
-			bytes -= bytes_count;
+			bytes -= sg[i].length;
 		}
 	}
 
@@ -578,19 +562,14 @@ EXPORT_SYMBOL_GPL(af_alg_count_tsgl);
  * af_alg_pull_tsgl - Release the specified buffers from TX SGL
  *
  * If @dst is non-null, reassign the pages to @dst. The caller must release
- * the pages. If @dst_offset is given only reassign the pages to @dst starting
- * at the @dst_offset (byte). The caller must ensure that @dst is large
- * enough (e.g. by using af_alg_count_tsgl with the same offset).
+ * the pages.
  *
  * @sk: socket of connection to user space
  * @used: Number of bytes to pull from TX SGL
  * @dst: If non-NULL, buffer is reassigned to dst SGL instead of releasing. The
  *	 caller must release the buffers in dst.
- * @dst_offset: Reassign the TX SGL from given offset. All buffers before
- *	        reaching the offset is released.
  */
-void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
-		      size_t dst_offset)
+void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst)
 {
 	struct alg_sock *ask = alg_sk(sk);
 	struct af_alg_ctx *ctx = ask->private;
@@ -615,18 +594,10 @@ void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
 			 * SG entries in dst.
 			 */
 			if (dst) {
-				if (dst_offset >= plen) {
-					/* discard page before offset */
-					dst_offset -= plen;
-				} else {
-					/* reassign page to dst after offset */
-					get_page(page);
-					sg_set_page(dst + j, page,
-						    plen - dst_offset,
-						    sg[i].offset + dst_offset);
-					dst_offset = 0;
-					j++;
-				}
+				/* reassign page to dst after offset */
+				get_page(page);
+				sg_set_page(dst + j, page, plen, sg[i].offset);
+				j++;
 			}
 
 			sg[i].length -= plen;

crypto/algif_aead.c

@@ -26,7 +26,6 @@
 #include <crypto/internal/aead.h>
 #include <crypto/scatterwalk.h>
 #include <crypto/if_alg.h>
-#include <crypto/skcipher.h>
 #include <crypto/null.h>
 #include <linux/init.h>
 #include <linux/list.h>
@@ -96,9 +95,8 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 	struct aead_tfm *aeadc = pask->private;
 	struct crypto_aead *tfm = aeadc->aead;
 	struct crypto_sync_skcipher *null_tfm = aeadc->null_tfm;
-	unsigned int i, as = crypto_aead_authsize(tfm);
+	unsigned int as = crypto_aead_authsize(tfm);
 	struct af_alg_async_req *areq;
-	struct af_alg_tsgl *tsgl, *tmp;
 	struct scatterlist *rsgl_src, *tsgl_src = NULL;
 	int err = 0;
 	size_t used = 0;		/* [in]  TX bufs to be en/decrypted */
@@ -178,23 +176,24 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 		outlen -= less;
 	}
 
+	/*
+	 * Create a per request TX SGL for this request which tracks the
+	 * SG entries from the global TX SGL.
+	 */
 	processed = used + ctx->aead_assoclen;
-	list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
-		for (i = 0; i < tsgl->cur; i++) {
-			struct scatterlist *process_sg = tsgl->sg + i;
-
-			if (!(process_sg->length) || !sg_page(process_sg))
-				continue;
-			tsgl_src = process_sg;
-			break;
-		}
-		if (tsgl_src)
-			break;
-	}
-	if (processed && !tsgl_src) {
-		err = -EFAULT;
+	areq->tsgl_entries = af_alg_count_tsgl(sk, processed);
+	if (!areq->tsgl_entries)
+		areq->tsgl_entries = 1;
+	areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
+					         areq->tsgl_entries),
+				  GFP_KERNEL);
+	if (!areq->tsgl) {
+		err = -ENOMEM;
 		goto free;
 	}
+	sg_init_table(areq->tsgl, areq->tsgl_entries);
+	af_alg_pull_tsgl(sk, processed, areq->tsgl);
+	tsgl_src = areq->tsgl;
 
 	/*
 	 * Copy of AAD from source to destination
@@ -203,81 +202,18 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 	 * when user space uses an in-place cipher operation, the kernel
 	 * will copy the data as it does not see whether such in-place operation
 	 * is initiated.
-	 *
-	 * To ensure efficiency, the following implementation ensure that the
-	 * ciphers are invoked to perform a crypto operation in-place. This
-	 * is achieved by memory management specified as follows.
 	 */
 
 	/* Use the RX SGL as source (and destination) for crypto op. */
 	rsgl_src = areq->first_rsgl.sgl.sg;
 
-	if (ctx->enc) {
-		/*
-		 * Encryption operation - The in-place cipher operation is
-		 * achieved by the following operation:
-		 *
-		 * TX SGL: AAD || PT
-		 *	    |	   |
-		 *	    | copy |
-		 *	    v	   v
-		 * RX SGL: AAD || PT || Tag
-		 */
-		err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
-					   areq->first_rsgl.sgl.sg, processed);
-		if (err)
-			goto free;
-		af_alg_pull_tsgl(sk, processed, NULL, 0);
-	} else {
-		/*
-		 * Decryption operation - To achieve an in-place cipher
-		 * operation, the following  SGL structure is used:
-		 *
-		 * TX SGL: AAD || CT || Tag
-		 *	    |	   |	 ^
-		 *	    | copy |	 | Create SGL link.
-		 *	    v	   v	 |
-		 * RX SGL: AAD || CT ----+
-		 */
-
-		 /* Copy AAD || CT to RX SGL buffer for in-place operation. */
-		err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
-					   areq->first_rsgl.sgl.sg, outlen);
-		if (err)
-			goto free;
-
-		/* Create TX SGL for tag and chain it to RX SGL. */
-		areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
-						       processed - as);
-		if (!areq->tsgl_entries)
-			areq->tsgl_entries = 1;
-		areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
-							 areq->tsgl_entries),
-					  GFP_KERNEL);
-		if (!areq->tsgl) {
-			err = -ENOMEM;
-			goto free;
-		}
-		sg_init_table(areq->tsgl, areq->tsgl_entries);
-
-		/* Release TX SGL, except for tag data and reassign tag data. */
-		af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
-
-		/* chain the areq TX SGL holding the tag with RX SGL */
-		if (usedpages) {
-			/* RX SGL present */
-			struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
-
-			sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
-			sg_chain(sgl_prev->sg, sgl_prev->npages + 1,
-				 areq->tsgl);
-		} else
-			/* no RX SGL present (e.g. authentication only) */
-			rsgl_src = areq->tsgl;
-	}
+	err = crypto_aead_copy_sgl(null_tfm, tsgl_src, rsgl_src,
+				   ctx->aead_assoclen);
+	if (err)
+		goto free;
 
 	/* Initialize the crypto operation */
-	aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
+	aead_request_set_crypt(&areq->cra_u.aead_req, tsgl_src,
 			       areq->first_rsgl.sgl.sg, used, ctx->iv);
 	aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
 	aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
@@ -526,7 +462,7 @@ static void aead_sock_destruct(struct sock *sk)
 	struct crypto_aead *tfm = aeadc->aead;
 	unsigned int ivlen = crypto_aead_ivsize(tfm);
 
-	af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
+	af_alg_pull_tsgl(sk, ctx->used, NULL);
 	sock_kzfree_s(sk, ctx->iv, ivlen);
 	sock_kfree_s(sk, ctx, ctx->len);
 	af_alg_release_parent(sk);

crypto/algif_skcipher.c

@@ -89,7 +89,7 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
 	 * Create a per request TX SGL for this request which tracks the
 	 * SG entries from the global TX SGL.
 	 */
-	areq->tsgl_entries = af_alg_count_tsgl(sk, len, 0);
+	areq->tsgl_entries = af_alg_count_tsgl(sk, len);
 	if (!areq->tsgl_entries)
 		areq->tsgl_entries = 1;
 	areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
@@ -100,7 +100,7 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
 		goto free;
 	}
 	sg_init_table(areq->tsgl, areq->tsgl_entries);
-	af_alg_pull_tsgl(sk, len, areq->tsgl, 0);
+	af_alg_pull_tsgl(sk, len, areq->tsgl);
 
 	/* Initialize the crypto operation */
 	skcipher_request_set_tfm(&areq->cra_u.skcipher_req, tfm);
@@ -313,7 +313,7 @@ static void skcipher_sock_destruct(struct sock *sk)
 	struct alg_sock *pask = alg_sk(psk);
 	struct crypto_skcipher *tfm = pask->private;
 
-	af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
+	af_alg_pull_tsgl(sk, ctx->used, NULL);
 	sock_kzfree_s(sk, ctx->iv, crypto_skcipher_ivsize(tfm));
 	sock_kfree_s(sk, ctx, ctx->len);
 	af_alg_release_parent(sk);

include/crypto/if_alg.h

@@ -226,9 +226,8 @@ static inline bool af_alg_readable(struct sock *sk)
 	return PAGE_SIZE <= af_alg_rcvbuf(sk);
 }
 
-unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes, size_t offset);
-void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
-		      size_t dst_offset);
+unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes);
+void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst);
 void af_alg_wmem_wakeup(struct sock *sk);
 int af_alg_wait_for_data(struct sock *sk, unsigned flags, unsigned min);
 int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,