ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set,
a user fault may trigger show_pte() without any lock.
If another thread in the same process concurrently calls munmap(),
the page table pages may be freed while show_pte() is still traversing
them, causing a use-after-free in show_pte().

If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table
of PMD are freed when show_pte() is running.

Acquire mmap_write_lock() around show_pte() for user faults to fix the
contention.

For user faults, additionally restrict that show_pte() is called only
when the addr is a user-space address (addr < TASK_SIZE). This is because
the lock of tsk->mm only protects the virtual memory of user address space,
furthermore, dumping the page tables of a kernel-space address for user
faults is unnecessary and may have security implications.

Keep everything unchanged for kernel faults, because the kernel is
already in the "oops" state, acquiring a lock may risk a deadlock.

Co-developed-by: Qi Xi <xiqi2@huawei.com>

Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults")
Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 299 insertions, 0 deletions

diff --git a/fs/jffs2/malloc.c b/fs/jffs2/malloc.c
new file mode 100644
index 000000000..411de8b36
--- /dev/null
+++ b/fs/jffs2/malloc.c
@@ -0,0 +1,299 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/jffs2.h>
+#include "nodelist.h"
+
+/* These are initialised to NULL in the kernel startup code.
+   If you're porting to other operating systems, beware */
+static struct kmem_cache *full_dnode_slab;
+static struct kmem_cache *raw_dirent_slab;
+static struct kmem_cache *raw_inode_slab;
+static struct kmem_cache *tmp_dnode_info_slab;
+static struct kmem_cache *raw_node_ref_slab;
+static struct kmem_cache *node_frag_slab;
+static struct kmem_cache *inode_cache_slab;
+#ifdef CONFIG_JFFS2_FS_XATTR
+static struct kmem_cache *xattr_datum_cache;
+static struct kmem_cache *xattr_ref_cache;
+#endif
+
+int __init jffs2_create_slab_caches(void)
+{
+	full_dnode_slab = KMEM_CACHE(jffs2_full_dnode, 0);
+	if (!full_dnode_slab)
+		goto err;
+
+	raw_dirent_slab = KMEM_CACHE(jffs2_raw_dirent, SLAB_HWCACHE_ALIGN);
+	if (!raw_dirent_slab)
+		goto err;
+
+	raw_inode_slab = KMEM_CACHE(jffs2_raw_inode, SLAB_HWCACHE_ALIGN);
+	if (!raw_inode_slab)
+		goto err;
+
+	tmp_dnode_info_slab = KMEM_CACHE(jffs2_tmp_dnode_info, 0);
+	if (!tmp_dnode_info_slab)
+		goto err;
+
+	raw_node_ref_slab = kmem_cache_create("jffs2_refblock",
+					      sizeof(struct jffs2_raw_node_ref) * (REFS_PER_BLOCK + 1),
+					      0, 0, NULL);
+	if (!raw_node_ref_slab)
+		goto err;
+
+	node_frag_slab = KMEM_CACHE(jffs2_node_frag, 0);
+	if (!node_frag_slab)
+		goto err;
+
+	inode_cache_slab = KMEM_CACHE(jffs2_inode_cache, 0);
+	if (!inode_cache_slab)
+		goto err;
+
+#ifdef CONFIG_JFFS2_FS_XATTR
+	xattr_datum_cache = KMEM_CACHE(jffs2_xattr_datum, 0);
+	if (!xattr_datum_cache)
+		goto err;
+
+	xattr_ref_cache = KMEM_CACHE(jffs2_xattr_ref, 0);
+	if (!xattr_ref_cache)
+		goto err;
+#endif
+
+	return 0;
+ err:
+	jffs2_destroy_slab_caches();
+	return -ENOMEM;
+}
+
+void jffs2_destroy_slab_caches(void)
+{
+	kmem_cache_destroy(full_dnode_slab);
+	kmem_cache_destroy(raw_dirent_slab);
+	kmem_cache_destroy(raw_inode_slab);
+	kmem_cache_destroy(tmp_dnode_info_slab);
+	kmem_cache_destroy(raw_node_ref_slab);
+	kmem_cache_destroy(node_frag_slab);
+	kmem_cache_destroy(inode_cache_slab);
+#ifdef CONFIG_JFFS2_FS_XATTR
+	kmem_cache_destroy(xattr_datum_cache);
+	kmem_cache_destroy(xattr_ref_cache);
+#endif
+}
+
+struct jffs2_full_dirent *jffs2_alloc_full_dirent(int namesize)
+{
+	struct jffs2_full_dirent *ret;
+	ret = kmalloc(sizeof(struct jffs2_full_dirent) + namesize, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_full_dirent(struct jffs2_full_dirent *x)
+{
+	dbg_memalloc("%p\n", x);
+	kfree(x);
+}
+
+struct jffs2_full_dnode *jffs2_alloc_full_dnode(void)
+{
+	struct jffs2_full_dnode *ret;
+	ret = kmem_cache_alloc(full_dnode_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_full_dnode(struct jffs2_full_dnode *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(full_dnode_slab, x);
+}
+
+struct jffs2_raw_dirent *jffs2_alloc_raw_dirent(void)
+{
+	struct jffs2_raw_dirent *ret;
+	ret = kmem_cache_alloc(raw_dirent_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_raw_dirent(struct jffs2_raw_dirent *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(raw_dirent_slab, x);
+}
+
+struct jffs2_raw_inode *jffs2_alloc_raw_inode(void)
+{
+	struct jffs2_raw_inode *ret;
+	ret = kmem_cache_alloc(raw_inode_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_raw_inode(struct jffs2_raw_inode *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(raw_inode_slab, x);
+}
+
+struct jffs2_tmp_dnode_info *jffs2_alloc_tmp_dnode_info(void)
+{
+	struct jffs2_tmp_dnode_info *ret;
+	ret = kmem_cache_alloc(tmp_dnode_info_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n",
+		ret);
+	return ret;
+}
+
+void jffs2_free_tmp_dnode_info(struct jffs2_tmp_dnode_info *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(tmp_dnode_info_slab, x);
+}
+
+static struct jffs2_raw_node_ref *jffs2_alloc_refblock(void)
+{
+	struct jffs2_raw_node_ref *ret;
+
+	ret = kmem_cache_alloc(raw_node_ref_slab, GFP_KERNEL);
+	if (ret) {
+		int i = 0;
+		for (i=0; i < REFS_PER_BLOCK; i++) {
+			ret[i].flash_offset = REF_EMPTY_NODE;
+			ret[i].next_in_ino = NULL;
+		}
+		ret[i].flash_offset = REF_LINK_NODE;
+		ret[i].next_in_ino = NULL;
+	}
+	return ret;
+}
+
+int jffs2_prealloc_raw_node_refs(struct jffs2_sb_info *c,
+				 struct jffs2_eraseblock *jeb, int nr)
+{
+	struct jffs2_raw_node_ref **p, *ref;
+	int i = nr;
+
+	dbg_memalloc("%d\n", nr);
+
+	p = &jeb->last_node;
+	ref = *p;
+
+	dbg_memalloc("Reserving %d refs for block @0x%08x\n", nr, jeb->offset);
+
+	/* If jeb->last_node is really a valid node then skip over it */
+	if (ref && ref->flash_offset != REF_EMPTY_NODE)
+		ref++;
+
+	while (i) {
+		if (!ref) {
+			dbg_memalloc("Allocating new refblock linked from %p\n", p);
+			ref = *p = jffs2_alloc_refblock();
+			if (!ref)
+				return -ENOMEM;
+		}
+		if (ref->flash_offset == REF_LINK_NODE) {
+			p = &ref->next_in_ino;
+			ref = *p;
+			continue;
+		}
+		i--;
+		ref++;
+	}
+	jeb->allocated_refs = nr;
+
+	dbg_memalloc("Reserved %d refs for block @0x%08x, last_node is %p (%08x,%p)\n",
+		  nr, jeb->offset, jeb->last_node, jeb->last_node->flash_offset,
+		  jeb->last_node->next_in_ino);
+
+	return 0;
+}
+
+void jffs2_free_refblock(struct jffs2_raw_node_ref *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(raw_node_ref_slab, x);
+}
+
+struct jffs2_node_frag *jffs2_alloc_node_frag(void)
+{
+	struct jffs2_node_frag *ret;
+	ret = kmem_cache_alloc(node_frag_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_node_frag(struct jffs2_node_frag *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(node_frag_slab, x);
+}
+
+struct jffs2_inode_cache *jffs2_alloc_inode_cache(void)
+{
+	struct jffs2_inode_cache *ret;
+	ret = kmem_cache_alloc(inode_cache_slab, GFP_KERNEL);
+	dbg_memalloc("%p\n", ret);
+	return ret;
+}
+
+void jffs2_free_inode_cache(struct jffs2_inode_cache *x)
+{
+	dbg_memalloc("%p\n", x);
+	kmem_cache_free(inode_cache_slab, x);
+}
+
+#ifdef CONFIG_JFFS2_FS_XATTR
+struct jffs2_xattr_datum *jffs2_alloc_xattr_datum(void)
+{
+	struct jffs2_xattr_datum *xd;
+	xd = kmem_cache_zalloc(xattr_datum_cache, GFP_KERNEL);
+	dbg_memalloc("%p\n", xd);
+	if (!xd)
+		return NULL;
+
+	xd->class = RAWNODE_CLASS_XATTR_DATUM;
+	xd->node = (void *)xd;
+	INIT_LIST_HEAD(&xd->xindex);
+	return xd;
+}
+
+void jffs2_free_xattr_datum(struct jffs2_xattr_datum *xd)
+{
+	dbg_memalloc("%p\n", xd);
+	kmem_cache_free(xattr_datum_cache, xd);
+}
+
+struct jffs2_xattr_ref *jffs2_alloc_xattr_ref(void)
+{
+	struct jffs2_xattr_ref *ref;
+	ref = kmem_cache_zalloc(xattr_ref_cache, GFP_KERNEL);
+	dbg_memalloc("%p\n", ref);
+	if (!ref)
+		return NULL;
+
+	ref->class = RAWNODE_CLASS_XATTR_REF;
+	ref->node = (void *)ref;
+	return ref;
+}
+
+void jffs2_free_xattr_ref(struct jffs2_xattr_ref *ref)
+{
+	dbg_memalloc("%p\n", ref);
+	kmem_cache_free(xattr_ref_cache, ref);
+}
+#endif