apparmor: use zstd compression for profile data

Change the algorithm used by apparmor to compress profile data from
zlib to zstd, using the new zstd API introduced in 5.16.

Zstd provides a larger range of compression levels than zlib and
significantly better performance at the default level (for a relatively
small increase in compressed size).

The apparmor module parameter raw_data_compression_level is now clamped
to the minimum and maximum compression levels reported by the zstd
library. A compression level of 0 retains the previous behavior of
disabling policy compression instead of using zstd's behavior, which is
to use the default compression level.
Signed-off-by: Jon Tourville <jon.tourville@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/Kconfig

@@ -85,8 +85,8 @@ config SECURITY_APPARMOR_HASH_DEFAULT
 config SECURITY_APPARMOR_EXPORT_BINARY
 	bool "Allow exporting the raw binary policy"
 	depends on SECURITY_APPARMOR_INTROSPECT_POLICY
-	select ZLIB_INFLATE
-	select ZLIB_DEFLATE
+	select ZSTD_COMPRESS
+	select ZSTD_DECOMPRESS
 	default y
 	help
 	  This option allows reading back binary policy as it was loaded.

security/apparmor/apparmorfs.c

@@ -21,7 +21,7 @@
 #include <linux/fs.h>
 #include <linux/fs_context.h>
 #include <linux/poll.h>
-#include <linux/zlib.h>
+#include <linux/zstd.h>
 #include <uapi/linux/major.h>
 #include <uapi/linux/magic.h>
 
@@ -1297,42 +1297,30 @@ SEQ_RAWDATA_FOPS(revision);
 SEQ_RAWDATA_FOPS(hash);
 SEQ_RAWDATA_FOPS(compressed_size);
 
-static int deflate_decompress(char *src, size_t slen, char *dst, size_t dlen)
+static int decompress_zstd(char *src, size_t slen, char *dst, size_t dlen)
 {
 #ifdef CONFIG_SECURITY_APPARMOR_EXPORT_BINARY
-	if (aa_g_rawdata_compression_level != 0) {
-		int error = 0;
-		struct z_stream_s strm;
-
-		memset(&strm, 0, sizeof(strm));
-
-		strm.workspace = kvzalloc(zlib_inflate_workspacesize(), GFP_KERNEL);
-		if (!strm.workspace)
-			return -ENOMEM;
-
-		strm.next_in = src;
-		strm.avail_in = slen;
-
-		error = zlib_inflateInit(&strm);
-		if (error != Z_OK) {
-			error = -ENOMEM;
-			goto fail_inflate_init;
-		}
-
-		strm.next_out = dst;
-		strm.avail_out = dlen;
-
-		error = zlib_inflate(&strm, Z_FINISH);
-		if (error != Z_STREAM_END)
-			error = -EINVAL;
-		else
-			error = 0;
-
-		zlib_inflateEnd(&strm);
-fail_inflate_init:
-		kvfree(strm.workspace);
-
-		return error;
+	if (aa_g_rawdata_compression_level == 0) {
+		const size_t wksp_len = zstd_dctx_workspace_bound();
+		zstd_dctx *ctx;
+		void *wksp;
+		size_t out_len;
+		int ret = 0;
+
+		wksp = kvzalloc(wksp_len, GFP_KERNEL);
+		if (!wksp) {
+			ret = -ENOMEM;
+			goto cleanup;
+		}
+
+		out_len = zstd_decompress_dctx(ctx, dst, dlen, src, slen);
+		if (zstd_is_error(out_len)) {
+			ret = -EINVAL;
+			goto cleanup;
+		}
+cleanup:
+		kvfree(wksp);
+		return ret;
 	}
 #endif
 
@@ -1381,7 +1369,7 @@ static int rawdata_open(struct inode *inode, struct file *file)
 
 	private->loaddata = loaddata;
 
-	error = deflate_decompress(loaddata->data, loaddata->compressed_size,
+	error = decompress_zstd(loaddata->data, loaddata->compressed_size,
 				RAWDATA_F_DATA_BUF(private),
 				loaddata->size);
 	if (error)

security/apparmor/lsm.c

@@ -21,7 +21,7 @@
 #include <linux/user_namespace.h>
 #include <linux/netfilter_ipv4.h>
 #include <linux/netfilter_ipv6.h>
-#include <linux/zlib.h>
+#include <linux/zstd.h>
 #include <net/sock.h>
 #include <uapi/linux/mount.h>
 
@@ -1361,7 +1361,7 @@ module_param_named(export_binary, aa_g_export_binary, aabool, 0600);
 #endif
 
 /* policy loaddata compression level */
-int aa_g_rawdata_compression_level = Z_DEFAULT_COMPRESSION;
+int aa_g_rawdata_compression_level = ZSTD_CLEVEL_DEFAULT;
 module_param_named(rawdata_compression_level, aa_g_rawdata_compression_level,
 		   aacompressionlevel, 0400);
 
@@ -1543,9 +1543,9 @@ static int param_set_aacompressionlevel(const char *val,
 	error = param_set_int(val, kp);
 
 	aa_g_rawdata_compression_level = clamp(aa_g_rawdata_compression_level,
-					       Z_NO_COMPRESSION,
-					       Z_BEST_COMPRESSION);
-	pr_info("AppArmor: policy rawdata compression level set to %u\n",
+					       zstd_min_clevel(),
+					       zstd_max_clevel());
+	pr_info("AppArmor: policy rawdata compression level set to %d\n",
 		aa_g_rawdata_compression_level);
 
 	return error;

security/apparmor/policy_unpack.c

@@ -16,7 +16,7 @@
 #include <asm/unaligned.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
-#include <linux/zlib.h>
+#include <linux/zstd.h>
 
 #include "include/apparmor.h"
 #include "include/audit.h"
@@ -1059,81 +1059,73 @@ struct aa_load_ent *aa_load_ent_alloc(void)
 	return ent;
 }
 
-static int deflate_compress(const char *src, size_t slen, char **dst,
-			    size_t *dlen)
+static int compress_zstd(const char *src, size_t slen, char **dst, size_t *dlen)
 {
 #ifdef CONFIG_SECURITY_APPARMOR_EXPORT_BINARY
-	int error;
-	struct z_stream_s strm;
-	void *stgbuf, *dstbuf;
-	size_t stglen = deflateBound(slen);
-
-	memset(&strm, 0, sizeof(strm));
-
-	if (stglen < slen)
-		return -EFBIG;
-
-	strm.workspace = kvzalloc(zlib_deflate_workspacesize(MAX_WBITS,
-							     MAX_MEM_LEVEL),
-				  GFP_KERNEL);
-	if (!strm.workspace)
-		return -ENOMEM;
+	const zstd_parameters params =
+		zstd_get_params(aa_g_rawdata_compression_level, slen);
+	const size_t wksp_len = zstd_cctx_workspace_bound(&params.cParams);
+	void *wksp = NULL;
+	zstd_cctx *ctx = NULL;
+	size_t out_len = zstd_compress_bound(slen);
+	void *out = NULL;
+	int ret = 0;
 
-	error = zlib_deflateInit(&strm, aa_g_rawdata_compression_level);
-	if (error != Z_OK) {
-		error = -ENOMEM;
-		goto fail_deflate_init;
+	out = kvzalloc(out_len, GFP_KERNEL);
+	if (!out) {
+		ret = -ENOMEM;
+		goto cleanup;
 	}
 
-	stgbuf = kvzalloc(stglen, GFP_KERNEL);
-	if (!stgbuf) {
-		error = -ENOMEM;
-		goto fail_stg_alloc;
+	wksp = kvzalloc(wksp_len, GFP_KERNEL);
+	if (!wksp) {
+		ret = -ENOMEM;
+		goto cleanup;
 	}
 
-	strm.next_in = src;
-	strm.avail_in = slen;
-	strm.next_out = stgbuf;
-	strm.avail_out = stglen;
+	ctx = zstd_init_cctx(wksp, wksp_len);
+	if (!ctx) {
+		ret = -EINVAL;
+		goto cleanup;
+	}
 
-	error = zlib_deflate(&strm, Z_FINISH);
-	if (error != Z_STREAM_END) {
-		error = -EINVAL;
-		goto fail_deflate;
+	out_len = zstd_compress_cctx(ctx, out, out_len, src, slen, &params);
+	if (zstd_is_error(out_len)) {
+		ret = -EINVAL;
+		goto cleanup;
 	}
-	error = 0;
 
-	if (is_vmalloc_addr(stgbuf)) {
-		dstbuf = kvzalloc(strm.total_out, GFP_KERNEL);
-		if (dstbuf) {
-			memcpy(dstbuf, stgbuf, strm.total_out);
-			kvfree(stgbuf);
+	if (is_vmalloc_addr(out)) {
+		*dst = kvzalloc(out_len, GFP_KERNEL);
+		if (*dst) {
+			memcpy(*dst, out, out_len);
+			kvfree(out);
+			out = NULL;
 		}
-	} else
+	} else {
 		/*
 		 * If the staging buffer was kmalloc'd, then using krealloc is
 		 * probably going to be faster. The destination buffer will
 		 * always be smaller, so it's just shrunk, avoiding a memcpy
 		 */
-		dstbuf = krealloc(stgbuf, strm.total_out, GFP_KERNEL);
+		*dst = krealloc(out, out_len, GFP_KERNEL);
+	}
 
-	if (!dstbuf) {
-		error = -ENOMEM;
-		goto fail_deflate;
+	if (!*dst) {
+		ret = -ENOMEM;
+		goto cleanup;
 	}
 
-	*dst = dstbuf;
-	*dlen = strm.total_out;
+	*dlen = out_len;
 
-fail_stg_alloc:
-	zlib_deflateEnd(&strm);
-fail_deflate_init:
-	kvfree(strm.workspace);
-	return error;
+cleanup:
+	if (ret) {
+		kvfree(out);
+		*dst = NULL;
+	}
 
-fail_deflate:
-	kvfree(stgbuf);
-	goto fail_stg_alloc;
+	kvfree(wksp);
+	return ret;
 #else
 	*dlen = slen;
 	return 0;
@@ -1142,7 +1134,6 @@ static int deflate_compress(const char *src, size_t slen, char **dst,
 
 static int compress_loaddata(struct aa_loaddata *data)
 {
-
 	AA_BUG(data->compressed_size > 0);
 
 	/*
@@ -1151,7 +1142,7 @@ static int compress_loaddata(struct aa_loaddata *data)
 	 */
 	if (aa_g_rawdata_compression_level != 0) {
 		void *udata = data->data;
-		int error = deflate_compress(udata, data->size, &data->data,
+		int error = compress_zstd(udata, data->size, &data->data,
 					  &data->compressed_size);
 		if (error)
 			return error;