Merge tag 'pstore-v6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore updates from Kees Cook:

 - Greatly simplify compression support (Ard Biesheuvel)

 - Avoid crashes for corrupted offsets when prz size is 0 (Enlin Mu)

 - Expand range of usable record sizes (Yuxiao Zhang)

 - Fix kernel-doc warning (Matthew Wilcox)

* tag 'pstore-v6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore: Fix kernel-doc warning
  pstore: Support record sizes larger than kmalloc() limit
  pstore/ram: Check start of empty przs during init
  pstore: Replace crypto API compression with zlib_deflate library calls
  pstore: Remove worst-case compression size logic

fs/pstore/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 config PSTORE
 	tristate "Persistent store support"
-	select CRYPTO if PSTORE_COMPRESS
 	default n
 	help
 	   This option enables generic access to platform level
@@ -22,99 +21,18 @@ config PSTORE_DEFAULT_KMSG_BYTES
 	  Defines default size of pstore kernel log storage.
 	  Can be enlarged if needed, not recommended to shrink it.
 
-config PSTORE_DEFLATE_COMPRESS
-	tristate "DEFLATE (ZLIB) compression"
-	default y
-	depends on PSTORE
-	select CRYPTO_DEFLATE
-	help
-	  This option enables DEFLATE (also known as ZLIB) compression
-	  algorithm support.
-
-config PSTORE_LZO_COMPRESS
-	tristate "LZO compression"
-	depends on PSTORE
-	select CRYPTO_LZO
-	help
-	  This option enables LZO compression algorithm support.
-
-config PSTORE_LZ4_COMPRESS
-	tristate "LZ4 compression"
-	depends on PSTORE
-	select CRYPTO_LZ4
-	help
-	  This option enables LZ4 compression algorithm support.
-
-config PSTORE_LZ4HC_COMPRESS
-	tristate "LZ4HC compression"
-	depends on PSTORE
-	select CRYPTO_LZ4HC
-	help
-	  This option enables LZ4HC (high compression) mode algorithm.
-
-config PSTORE_842_COMPRESS
-	bool "842 compression"
-	depends on PSTORE
-	select CRYPTO_842
-	help
-	  This option enables 842 compression algorithm support.
-
-config PSTORE_ZSTD_COMPRESS
-	bool "zstd compression"
-	depends on PSTORE
-	select CRYPTO_ZSTD
-	help
-	  This option enables zstd compression algorithm support.
-
 config PSTORE_COMPRESS
-	def_bool y
+	bool "Pstore compression (deflate)"
 	depends on PSTORE
-	depends on PSTORE_DEFLATE_COMPRESS || PSTORE_LZO_COMPRESS ||	\
-		   PSTORE_LZ4_COMPRESS || PSTORE_LZ4HC_COMPRESS ||	\
-		   PSTORE_842_COMPRESS || PSTORE_ZSTD_COMPRESS
-
-choice
-	prompt "Default pstore compression algorithm"
-	depends on PSTORE_COMPRESS
+	select ZLIB_INFLATE
+	select ZLIB_DEFLATE
+	default y
 	help
-	  This option chooses the default active compression algorithm.
-	  This change be changed at boot with "pstore.compress=..." on
-	  the kernel command line.
-
-	  Currently, pstore has support for 6 compression algorithms:
-	  deflate, lzo, lz4, lz4hc, 842 and zstd.
-
-	  The default compression algorithm is deflate.
-
-	config PSTORE_DEFLATE_COMPRESS_DEFAULT
-		bool "deflate" if PSTORE_DEFLATE_COMPRESS
-
-	config PSTORE_LZO_COMPRESS_DEFAULT
-		bool "lzo" if PSTORE_LZO_COMPRESS
-
-	config PSTORE_LZ4_COMPRESS_DEFAULT
-		bool "lz4" if PSTORE_LZ4_COMPRESS
-
-	config PSTORE_LZ4HC_COMPRESS_DEFAULT
-		bool "lz4hc" if PSTORE_LZ4HC_COMPRESS
-
-	config PSTORE_842_COMPRESS_DEFAULT
-		bool "842" if PSTORE_842_COMPRESS
-
-	config PSTORE_ZSTD_COMPRESS_DEFAULT
-		bool "zstd" if PSTORE_ZSTD_COMPRESS
-
-endchoice
-
-config PSTORE_COMPRESS_DEFAULT
-	string
-	depends on PSTORE_COMPRESS
-	default "deflate" if PSTORE_DEFLATE_COMPRESS_DEFAULT
-	default "lzo" if PSTORE_LZO_COMPRESS_DEFAULT
-	default "lz4" if PSTORE_LZ4_COMPRESS_DEFAULT
-	default "lz4hc" if PSTORE_LZ4HC_COMPRESS_DEFAULT
-	default "842" if PSTORE_842_COMPRESS_DEFAULT
-	default "zstd" if PSTORE_ZSTD_COMPRESS_DEFAULT
+	  Whether pstore records should be compressed before being written to
+	  the backing store. This is implemented using the zlib 'deflate'
+	  algorithm, using the library implementation instead of using the full
+	  blown crypto API. This reduces the risk of secondary oopses or other
+	  problems while pstore is recording panic metadata.
 
 config PSTORE_CONSOLE
 	bool "Log kernel console messages"

fs/pstore/inode.c

@@ -54,7 +54,7 @@ static void free_pstore_private(struct pstore_private *private)
 	if (!private)
 		return;
 	if (private->record) {
-		kfree(private->record->buf);
+		kvfree(private->record->buf);
 		kfree(private->record->priv);
 		kfree(private->record);
 	}

fs/pstore/platform.c

@@ -14,24 +14,17 @@
 #include <linux/init.h>
 #include <linux/kmsg_dump.h>
 #include <linux/console.h>
+#include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/pstore.h>
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-#include <linux/lzo.h>
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-#include <linux/lz4.h>
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-#include <linux/zstd.h>
-#endif
-#include <linux/crypto.h>
 #include <linux/string.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/jiffies.h>
+#include <linux/vmalloc.h>
 #include <linux/workqueue.h>
+#include <linux/zlib.h>
 
 #include "internal.h"
 
@@ -80,12 +73,21 @@ static char *backend;
 module_param(backend, charp, 0444);
 MODULE_PARM_DESC(backend, "specific backend to use");
 
-static char *compress =
-#ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
-		CONFIG_PSTORE_COMPRESS_DEFAULT;
-#else
-		NULL;
-#endif
+/*
+ * pstore no longer implements compression via the crypto API, and only
+ * supports zlib deflate compression implemented using the zlib library
+ * interface. This removes additional complexity which is hard to justify for a
+ * diagnostic facility that has to operate in conditions where the system may
+ * have become unstable. Zlib deflate is comparatively small in terms of code
+ * size, and compresses ASCII text comparatively well. In terms of compression
+ * speed, deflate is not the best performer but for recording the log output on
+ * a kernel panic, this is not considered critical.
+ *
+ * The only remaining arguments supported by the compress= module parameter are
+ * 'deflate' and 'none'. To retain compatibility with existing installations,
+ * all other values are logged and replaced with 'deflate'.
+ */
+static char *compress = "deflate";
 module_param(compress, charp, 0444);
 MODULE_PARM_DESC(compress, "compression to use");
 
@@ -94,16 +96,9 @@ unsigned long kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
 module_param(kmsg_bytes, ulong, 0444);
 MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)");
 
-/* Compression parameters */
-static struct crypto_comp *tfm;
-
-struct pstore_zbackend {
-	int (*zbufsize)(size_t size);
-	const char *name;
-};
+static void *compress_workspace;
 
 static char *big_oops_buf;
-static size_t big_oops_buf_sz;
 
 void pstore_set_kmsg_bytes(int bytes)
 {
@@ -168,206 +163,89 @@ static bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
 	}
 }
 
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
-static int zbufsize_deflate(size_t size)
-{
-	size_t cmpr;
-
-	switch (size) {
-	/* buffer range for efivars */
-	case 1000 ... 2000:
-		cmpr = 56;
-		break;
-	case 2001 ... 3000:
-		cmpr = 54;
-		break;
-	case 3001 ... 3999:
-		cmpr = 52;
-		break;
-	/* buffer range for nvram, erst */
-	case 4000 ... 10000:
-		cmpr = 45;
-		break;
-	default:
-		cmpr = 60;
-		break;
-	}
-
-	return (size * 100) / cmpr;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-static int zbufsize_lzo(size_t size)
-{
-	return lzo1x_worst_compress(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-static int zbufsize_lz4(size_t size)
-{
-	return LZ4_compressBound(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
-static int zbufsize_842(size_t size)
-{
-	return size;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-static int zbufsize_zstd(size_t size)
-{
-	return zstd_compress_bound(size);
-}
-#endif
-
-static const struct pstore_zbackend *zbackend __ro_after_init;
-
-static const struct pstore_zbackend zbackends[] = {
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
-	{
-		.zbufsize	= zbufsize_deflate,
-		.name		= "deflate",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lzo,
-		.name		= "lzo",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lz4,
-		.name		= "lz4",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lz4,
-		.name		= "lz4hc",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
-	{
-		.zbufsize	= zbufsize_842,
-		.name		= "842",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-	{
-		.zbufsize	= zbufsize_zstd,
-		.name		= "zstd",
-	},
-#endif
-	{ }
-};
-
 static int pstore_compress(const void *in, void *out,
 			   unsigned int inlen, unsigned int outlen)
 {
+	struct z_stream_s zstream = {
+		.next_in	= in,
+		.avail_in	= inlen,
+		.next_out	= out,
+		.avail_out	= outlen,
+		.workspace	= compress_workspace,
+	};
 	int ret;
 
 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS))
 		return -EINVAL;
 
-	ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
-	if (ret) {
-		pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
-		return ret;
-	}
+	ret = zlib_deflateInit2(&zstream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
+				-MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY);
+	if (ret != Z_OK)
+		return -EINVAL;
+
+	ret = zlib_deflate(&zstream, Z_FINISH);
+	if (ret != Z_STREAM_END)
+		return -EINVAL;
+
+	ret = zlib_deflateEnd(&zstream);
+	if (ret != Z_OK)
+		pr_warn_once("zlib_deflateEnd() failed: %d\n", ret);
 
-	return outlen;
+	return zstream.total_out;
 }
 
 static void allocate_buf_for_compression(void)
 {
-	struct crypto_comp *ctx;
-	int size;
 	char *buf;
 
-	/* Skip if not built-in or compression backend not selected yet. */
-	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
-		return;
-
-	/* Skip if no pstore backend yet or compression init already done. */
-	if (!psinfo || tfm)
-		return;
-
-	if (!crypto_has_comp(zbackend->name, 0, 0)) {
-		pr_err("Unknown compression: %s\n", zbackend->name);
+	/* Skip if not built-in or compression disabled. */
+	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !compress ||
+	    !strcmp(compress, "none")) {
+		compress = NULL;
 		return;
 	}
 
-	size = zbackend->zbufsize(psinfo->bufsize);
-	if (size <= 0) {
-		pr_err("Invalid compression size for %s: %d\n",
-		       zbackend->name, size);
-		return;
+	if (strcmp(compress, "deflate")) {
+		pr_err("Unsupported compression '%s', falling back to deflate\n",
+		       compress);
+		compress = "deflate";
 	}
 
-	buf = kmalloc(size, GFP_KERNEL);
+	/*
+	 * The compression buffer only needs to be as large as the maximum
+	 * uncompressed record size, since any record that would be expanded by
+	 * compression is just stored uncompressed.
+	 */
+	buf = kvzalloc(psinfo->bufsize, GFP_KERNEL);
 	if (!buf) {
-		pr_err("Failed %d byte compression buffer allocation for: %s\n",
-		       size, zbackend->name);
+		pr_err("Failed %zu byte compression buffer allocation for: %s\n",
+		       psinfo->bufsize, compress);
 		return;
 	}
 
-	ctx = crypto_alloc_comp(zbackend->name, 0, 0);
-	if (IS_ERR_OR_NULL(ctx)) {
-		kfree(buf);
-		pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
-		       PTR_ERR(ctx));
+	compress_workspace =
+		vmalloc(zlib_deflate_workspacesize(MAX_WBITS, DEF_MEM_LEVEL));
+	if (!compress_workspace) {
+		pr_err("Failed to allocate zlib deflate workspace\n");
+		kvfree(buf);
 		return;
 	}
 
 	/* A non-NULL big_oops_buf indicates compression is available. */
-	tfm = ctx;
-	big_oops_buf_sz = size;
 	big_oops_buf = buf;
 
-	pr_info("Using crash dump compression: %s\n", zbackend->name);
+	pr_info("Using crash dump compression: %s\n", compress);
 }
 
 static void free_buf_for_compression(void)
 {
-	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
-		crypto_free_comp(tfm);
-		tfm = NULL;
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress_workspace) {
+		vfree(compress_workspace);
+		compress_workspace = NULL;
 	}
-	kfree(big_oops_buf);
-	big_oops_buf = NULL;
-	big_oops_buf_sz = 0;
-}
 
-/*
- * Called when compression fails, since the printk buffer
- * would be fetched for compression calling it again when
- * compression fails would have moved the iterator of
- * printk buffer which results in fetching old contents.
- * Copy the recent messages from big_oops_buf to psinfo->buf
- */
-static size_t copy_kmsg_to_buffer(int hsize, size_t len)
-{
-	size_t total_len;
-	size_t diff;
-
-	total_len = hsize + len;
-
-	if (total_len > psinfo->bufsize) {
-		diff = total_len - psinfo->bufsize + hsize;
-		memcpy(psinfo->buf, big_oops_buf, hsize);
-		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
-					psinfo->bufsize - hsize);
-		total_len = psinfo->bufsize;
-	} else
-		memcpy(psinfo->buf, big_oops_buf, total_len);
-
-	return total_len;
+	kvfree(big_oops_buf);
+	big_oops_buf = NULL;
 }
 
 void pstore_record_init(struct pstore_record *record,
@@ -426,13 +304,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		record.part = part;
 		record.buf = psinfo->buf;
 
-		if (big_oops_buf) {
-			dst = big_oops_buf;
-			dst_size = big_oops_buf_sz;
-		} else {
-			dst = psinfo->buf;
-			dst_size = psinfo->bufsize;
-		}
+		dst = big_oops_buf ?: psinfo->buf;
+		dst_size = psinfo->bufsize;
 
 		/* Write dump header. */
 		header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
@@ -453,8 +326,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 				record.compressed = true;
 				record.size = zipped_len;
 			} else {
-				record.size = copy_kmsg_to_buffer(header_size,
-								  dump_size);
+				record.size = header_size + dump_size;
+				memcpy(psinfo->buf, dst, record.size);
 			}
 		} else {
 			record.size = header_size + dump_size;
@@ -549,7 +422,7 @@ static int pstore_write_user_compat(struct pstore_record *record,
 	if (record->buf)
 		return -EINVAL;
 
-	record->buf = memdup_user(buf, record->size);
+	record->buf = vmemdup_user(buf, record->size);
 	if (IS_ERR(record->buf)) {
 		ret = PTR_ERR(record->buf);
 		goto out;
@@ -557,7 +430,7 @@ static int pstore_write_user_compat(struct pstore_record *record,
 
 	ret = record->psi->write(record);
 
-	kfree(record->buf);
+	kvfree(record->buf);
 out:
 	record->buf = NULL;
 
@@ -681,7 +554,8 @@ void pstore_unregister(struct pstore_info *psi)
 }
 EXPORT_SYMBOL_GPL(pstore_unregister);
 
-static void decompress_record(struct pstore_record *record)
+static void decompress_record(struct pstore_record *record,
+			      struct z_stream_s *zstream)
 {
 	int ret;
 	int unzipped_len;
@@ -697,40 +571,50 @@ static void decompress_record(struct pstore_record *record)
 	}
 
 	/* Missing compression buffer means compression was not initialized. */
-	if (!big_oops_buf) {
+	if (!zstream->workspace) {
 		pr_warn("no decompression method initialized!\n");
 		return;
 	}
 
+	ret = zlib_inflateReset(zstream);
+	if (ret != Z_OK) {
+		pr_err("zlib_inflateReset() failed, ret = %d!\n", ret);
+		return;
+	}
+
 	/* Allocate enough space to hold max decompression and ECC. */
-	unzipped_len = big_oops_buf_sz;
-	workspace = kmalloc(unzipped_len + record->ecc_notice_size,
-			    GFP_KERNEL);
+	workspace = kvzalloc(psinfo->bufsize + record->ecc_notice_size,
+			     GFP_KERNEL);
 	if (!workspace)
 		return;
 
-	/* After decompression "unzipped_len" is almost certainly smaller. */
-	ret = crypto_comp_decompress(tfm, record->buf, record->size,
-					  workspace, &unzipped_len);
-	if (ret) {
-		pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
-		kfree(workspace);
+	zstream->next_in	= record->buf;
+	zstream->avail_in	= record->size;
+	zstream->next_out	= workspace;
+	zstream->avail_out	= psinfo->bufsize;
+
+	ret = zlib_inflate(zstream, Z_FINISH);
+	if (ret != Z_STREAM_END) {
+		pr_err("zlib_inflate() failed, ret = %d!\n", ret);
+		kvfree(workspace);
 		return;
 	}
 
+	unzipped_len = zstream->total_out;
+
 	/* Append ECC notice to decompressed buffer. */
 	memcpy(workspace + unzipped_len, record->buf + record->size,
 	       record->ecc_notice_size);
 
 	/* Copy decompressed contents into an minimum-sized allocation. */
-	unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
-			   GFP_KERNEL);
-	kfree(workspace);
+	unzipped = kvmemdup(workspace, unzipped_len + record->ecc_notice_size,
+			    GFP_KERNEL);
+	kvfree(workspace);
 	if (!unzipped)
 		return;
 
 	/* Swap out compressed contents with decompressed contents. */
-	kfree(record->buf);
+	kvfree(record->buf);
 	record->buf = unzipped;
 	record->size = unzipped_len;
 	record->compressed = false;
@@ -747,10 +631,17 @@ void pstore_get_backend_records(struct pstore_info *psi,
 {
 	int failed = 0;
 	unsigned int stop_loop = 65536;
+	struct z_stream_s zstream = {};
 
 	if (!psi || !root)
 		return;
 
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
+		zstream.workspace = kvmalloc(zlib_inflate_workspacesize(),
+					     GFP_KERNEL);
+		zlib_inflateInit2(&zstream, -DEF_WBITS);
+	}
+
 	mutex_lock(&psi->read_mutex);
 	if (psi->open && psi->open(psi))
 		goto out;
@@ -779,11 +670,11 @@ void pstore_get_backend_records(struct pstore_info *psi,
 			break;
 		}
 
-		decompress_record(record);
+		decompress_record(record, &zstream);
 		rc = pstore_mkfile(root, record);
 		if (rc) {
 			/* pstore_mkfile() did not take record, so free it. */
-			kfree(record->buf);
+			kvfree(record->buf);
 			kfree(record->priv);
 			kfree(record);
 			if (rc != -EEXIST || !quiet)
@@ -795,6 +686,12 @@ void pstore_get_backend_records(struct pstore_info *psi,
 out:
 	mutex_unlock(&psi->read_mutex);
 
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
+		if (zlib_inflateEnd(&zstream) != Z_OK)
+			pr_warn("zlib_inflateEnd() failed\n");
+		kvfree(zstream.workspace);
+	}
+
 	if (failed)
 		pr_warn("failed to create %d record(s) from '%s'\n",
 			failed, psi->name);
@@ -818,34 +715,10 @@ static void pstore_timefunc(struct timer_list *unused)
 	pstore_timer_kick();
 }
 
-static void __init pstore_choose_compression(void)
-{
-	const struct pstore_zbackend *step;
-
-	if (!compress)
-		return;
-
-	for (step = zbackends; step->name; step++) {
-		if (!strcmp(compress, step->name)) {
-			zbackend = step;
-			return;
-		}
-	}
-}
-
 static int __init pstore_init(void)
 {
 	int ret;
 
-	pstore_choose_compression();
-
-	/*
-	 * Check if any pstore backends registered earlier but did not
-	 * initialize compression because crypto was not ready. If so,
-	 * initialize compression now.
-	 */
-	allocate_buf_for_compression();
-
 	ret = pstore_init_fs();
 	if (ret)
 		free_buf_for_compression();

fs/pstore/ram.c

@@ -20,6 +20,7 @@
 #include <linux/compiler.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/mm.h>
 
 #include "internal.h"
 #include "ram_internal.h"
@@ -268,7 +269,7 @@ static ssize_t ramoops_pstore_read(struct pstore_record *record)
 	/* ECC correction notice */
 	record->ecc_notice_size = persistent_ram_ecc_string(prz, NULL, 0);
 
-	record->buf = kmalloc(size + record->ecc_notice_size + 1, GFP_KERNEL);
+	record->buf = kvzalloc(size + record->ecc_notice_size + 1, GFP_KERNEL);
 	if (record->buf == NULL) {
 		size = -ENOMEM;
 		goto out;
@@ -282,7 +283,7 @@ static ssize_t ramoops_pstore_read(struct pstore_record *record)
 
 out:
 	if (free_prz) {
-		kfree(prz->old_log);
+		kvfree(prz->old_log);
 		kfree(prz);
 	}
 
@@ -833,7 +834,7 @@ static int ramoops_probe(struct platform_device *pdev)
 	 */
 	if (cxt->pstore.flags & PSTORE_FLAGS_DMESG) {
 		cxt->pstore.bufsize = cxt->dprzs[0]->buffer_size;
-		cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
+		cxt->pstore.buf = kvzalloc(cxt->pstore.bufsize, GFP_KERNEL);
 		if (!cxt->pstore.buf) {
 			pr_err("cannot allocate pstore crash dump buffer\n");
 			err = -ENOMEM;
@@ -866,7 +867,7 @@ static int ramoops_probe(struct platform_device *pdev)
 	return 0;
 
 fail_buf:
-	kfree(cxt->pstore.buf);
+	kvfree(cxt->pstore.buf);
 fail_clear:
 	cxt->pstore.bufsize = 0;
 fail_init:
@@ -881,7 +882,7 @@ static void ramoops_remove(struct platform_device *pdev)
 
 	pstore_unregister(&cxt->pstore);
 
-	kfree(cxt->pstore.buf);
+	kvfree(cxt->pstore.buf);
 	cxt->pstore.bufsize = 0;
 
 	ramoops_free_przs(cxt);

fs/pstore/ram_core.c

@@ -17,6 +17,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>
+#include <linux/mm.h>
 #include <asm/page.h>
 
 #include "ram_internal.h"
@@ -24,12 +25,10 @@
 /**
  * struct persistent_ram_buffer - persistent circular RAM buffer
  *
- * @sig:
- *	signature to indicate header (PERSISTENT_RAM_SIG xor PRZ-type value)
- * @start:
- *	offset into @data where the beginning of the stored bytes begin
- * @size:
- *	number of valid bytes stored in @data
+ * @sig: Signature to indicate header (PERSISTENT_RAM_SIG xor PRZ-type value)
+ * @start: First valid byte in the buffer.
+ * @size: Number of valid bytes in the buffer.
+ * @data: The contents of the buffer.
  */
 struct persistent_ram_buffer {
 	uint32_t    sig;
@@ -301,7 +300,7 @@ void persistent_ram_save_old(struct persistent_ram_zone *prz)
 
 	if (!prz->old_log) {
 		persistent_ram_ecc_old(prz);
-		prz->old_log = kmalloc(size, GFP_KERNEL);
+		prz->old_log = kvzalloc(size, GFP_KERNEL);
 	}
 	if (!prz->old_log) {
 		pr_err("failed to allocate buffer\n");
@@ -385,7 +384,7 @@ void *persistent_ram_old(struct persistent_ram_zone *prz)
 
 void persistent_ram_free_old(struct persistent_ram_zone *prz)
 {
-	kfree(prz->old_log);
+	kvfree(prz->old_log);
 	prz->old_log = NULL;
 	prz->old_log_size = 0;
 }
@@ -519,7 +518,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
 	sig ^= PERSISTENT_RAM_SIG;
 
 	if (prz->buffer->sig == sig) {
-		if (buffer_size(prz) == 0) {
+		if (buffer_size(prz) == 0 && buffer_start(prz) == 0) {
 			pr_debug("found existing empty buffer\n");
 			return 0;
 		}