linux-hardening - Re: [PATCH] pstore: ramoops: support pmsg size larger than kmalloc limitation

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Date:   Fri, 30 Jun 2023 13:50:55 -0700
From:   Yuxiao Zhang <yuxiaozhang@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Tony Luck <tony.luck@...el.com>,
        "'Guilherme G . Piccoli'" <gpiccoli@...lia.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        wak@...gle.com, Added@...gle.com, size@...gle.com,
        details@...gle.com, to@...gle.com, commit@...gle.com,
        message@...gle.com, and@...gle.com, fixed@...gle.com,
        the@...gle.com, format.See@...gle.com, new@...gle.com,
        Yuxiao Zhang <yuxiaozhang@...gle.com>
Subject: Re: [PATCH] pstore: ramoops: support pmsg size larger than kmalloc limitation

Thanks,
-Yuxiao


>From cd3ec6155a3cf0e198afdf2d040c73ee146b696f Mon Sep 17 00:00:00 2001
From: Yuxiao Zhang <yuxiaozhang@...gle.com>
Date: Fri, 30 Jun 2023 10:45:21 -0700
Subject: [PATCH] pstore: ramoops: support pmsg size larger than kmalloc
 limitation

Current pmsg implementation is using kmalloc for pmsg record buffer,
which has max size limits of 2^(MAX_ORDER + PAGE_SHIFT). Currently even
we allocate enough space with pmsg-size, pmsg will still fail if the
file size is larger than what kmalloc allowed.

Since we don't need physical contiguous memory for pmsg buffer,
we can use kvmalloc to avoid such limitation.

Signed-off-by: Yuxiao Zhang <yuxiaozhang@...gle.com>
---
 fs/pstore/inode.c    | 2 +-
 fs/pstore/platform.c | 9 +++++----
 fs/pstore/ram.c      | 5 +++--
 fs/pstore/ram_core.c | 3 ++-
 4 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index ffbadb8b3032..df7fb2ad4599 100644
--- a/fs/pstore/inode.c
+++ b/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);
 	}
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index cbc0b468c1ab..f51e9460ac9d 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -32,6 +32,7 @@
 #include <linux/uaccess.h>
 #include <linux/jiffies.h>
 #include <linux/workqueue.h>
+#include <linux/mm.h>
 
 #include "internal.h"
 
@@ -549,7 +550,7 @@ 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 +558,7 @@ 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;
 
@@ -730,7 +731,7 @@ static void decompress_record(struct pstore_record *record)
 		return;
 
 	/* Swap out compressed contents with decompressed contents. */
-	kfree(record->buf);
+	kvfree(record->buf);
 	record->buf = unzipped;
 	record->size = unzipped_len;
 	record->compressed = false;
@@ -783,7 +784,7 @@ 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)
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index ade66dbe5f39..296465b14fa9 100644
--- a/fs/pstore/ram.c
+++ b/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 = kvmalloc(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);
 	}
 
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 966191d3a5ba..3453d493ec27 100644
--- a/fs/pstore/ram_core.c
+++ b/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"
@@ -385,7 +386,7 @@ 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;
 }
-- 
2.41.0.255.g8b1d071c50-goog