pstore: Support record sizes larger than kmalloc() limit

Currently pstore record buffers are allocated using kmalloc() which has
a maximum size based on page size. If a large "pmsg-size" module
parameter is specified, pmsg will fail to copy the contents since
memdup_user() is limited to kmalloc() allocation sizes.

Since we don't need physically contiguous memory for any of the pstore
record buffers, use kvzalloc() to avoid such limitations in the core of
pstore and in the ram backend, and explicitly read from userspace using
vmemdup_user(). This also means that any other backends that want to
(or do already) support larger record sizes will Just Work now.

Signed-off-by: Yuxiao Zhang <yuxiaozhang@google.com>
Link: https://lore.kernel.org/r/20230627202540.881909-2-yuxiaozhang@google.com
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 14 insertions, 13 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index aaa5e4e66db4..62356d542ef6 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -14,6 +14,7 @@
 #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>
 #include <linux/string.h>
@@ -215,7 +216,7 @@ static void allocate_buf_for_compression(void)
 	 * uncompressed record size, since any record that would be expanded by
 	 * compression is just stored uncompressed.
 	 */
-	buf = kmalloc(psinfo->bufsize, GFP_KERNEL);
+	buf = kvzalloc(psinfo->bufsize, GFP_KERNEL);
 	if (!buf) {
 		pr_err("Failed %zu byte compression buffer allocation for: %s\n",
 		       psinfo->bufsize, compress);
@@ -226,7 +227,7 @@ static void allocate_buf_for_compression(void)
 		vmalloc(zlib_deflate_workspacesize(MAX_WBITS, DEF_MEM_LEVEL));
 	if (!compress_workspace) {
 		pr_err("Failed to allocate zlib deflate workspace\n");
-		kfree(buf);
+		kvfree(buf);
 		return;
 	}
 
@@ -243,7 +244,7 @@ static void free_buf_for_compression(void)
 		compress_workspace = NULL;
 	}
 
-	kfree(big_oops_buf);
+	kvfree(big_oops_buf);
 	big_oops_buf = NULL;
 }
 
@@ -421,7 +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;
@@ -429,7 +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;
 
@@ -582,8 +583,8 @@ static void decompress_record(struct pstore_record *record,
 	}
 
 	/* Allocate enough space to hold max decompression and ECC. */
-	workspace = kmalloc(psinfo->bufsize + record->ecc_notice_size,
-			    GFP_KERNEL);
+	workspace = kvzalloc(psinfo->bufsize + record->ecc_notice_size,
+			     GFP_KERNEL);
 	if (!workspace)
 		return;
 
@@ -595,7 +596,7 @@ static void decompress_record(struct pstore_record *record,
 	ret = zlib_inflate(zstream, Z_FINISH);
 	if (ret != Z_STREAM_END) {
 		pr_err("zlib_inflate() failed, ret = %d!\n", ret);
-		kfree(workspace);
+		kvfree(workspace);
 		return;
 	}
 
@@ -606,14 +607,14 @@ static void decompress_record(struct pstore_record *record,
 	       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;
@@ -673,7 +674,7 @@ void pstore_get_backend_records(struct pstore_info *psi,
 		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)