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Message-Id: <20200506152114.50375-9-keescook@chromium.org>
Date: Wed, 6 May 2020 08:21:12 -0700
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
Luis Henriques <lhenriques@...e.com>
Subject: [PATCH 08/10] pstore: Add locking around superblock changes
Nothing was protecting changes to the pstorefs superblock. Add locking
and refactor away is_pstore_mounted(), instead using a helper to add a
way to safely lock the pstorefs root inode during filesystem changes.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
fs/pstore/inode.c | 65 +++++++++++++++++++++++++++++---------------
fs/pstore/internal.h | 1 -
fs/pstore/platform.c | 5 ++--
3 files changed, 45 insertions(+), 26 deletions(-)
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 5f08b21b7a46..e13482c8e180 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -31,6 +31,9 @@
static DEFINE_MUTEX(records_list_lock);
static LIST_HEAD(records_list);
+static DEFINE_MUTEX(pstore_sb_lock);
+static struct super_block *pstore_sb;
+
struct pstore_private {
struct list_head list;
struct pstore_record *record;
@@ -282,11 +285,25 @@ static const struct super_operations pstore_ops = {
.show_options = pstore_show_options,
};
-static struct super_block *pstore_sb;
-
-bool pstore_is_mounted(void)
+struct dentry *psinfo_lock_root(void)
{
- return pstore_sb != NULL;
+ struct dentry *root;
+
+ mutex_lock(&pstore_sb_lock);
+ /*
+ * Having no backend is fine -- no records appear.
+ * Not being mounted is fine -- nothing to do.
+ */
+ if (!psinfo || !pstore_sb) {
+ mutex_unlock(&pstore_sb_lock);
+ return NULL;
+ }
+
+ root = pstore_sb->s_root;
+ inode_lock(d_inode(root));
+ mutex_unlock(&pstore_sb_lock);
+
+ return root;
}
/*
@@ -303,20 +320,18 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
struct pstore_private *private, *pos;
size_t size = record->size + record->ecc_notice_size;
- WARN_ON(!inode_is_locked(d_inode(root)));
+ if (WARN_ON(!inode_is_locked(d_inode(root))))
+ return -EINVAL;
+ rc = -EEXIST;
+ /* Skip records that are already present in the filesystem. */
mutex_lock(&records_list_lock);
list_for_each_entry(pos, &records_list, list) {
if (pos->record->type == record->type &&
pos->record->id == record->id &&
- pos->record->psi == record->psi) {
- rc = -EEXIST;
- break;
- }
+ pos->record->psi == record->psi)
+ goto fail;
}
- mutex_unlock(&records_list_lock);
- if (rc)
- return rc;
rc = -ENOMEM;
inode = pstore_get_inode(root->d_sb);
@@ -346,7 +361,6 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
d_add(dentry, inode);
- mutex_lock(&records_list_lock);
list_add(&private->list, &records_list);
mutex_unlock(&records_list_lock);
@@ -356,8 +370,8 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
free_pstore_private(private);
fail_inode:
iput(inode);
-
fail:
+ mutex_unlock(&records_list_lock);
return rc;
}
@@ -369,16 +383,13 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
*/
void pstore_get_records(int quiet)
{
- struct pstore_info *psi = psinfo;
struct dentry *root;
- if (!psi || !pstore_sb)
+ root = psinfo_lock_root();
+ if (!root)
return;
- root = pstore_sb->s_root;
-
- inode_lock(d_inode(root));
- pstore_get_backend_records(psi, root, quiet);
+ pstore_get_backend_records(psinfo, root, quiet);
inode_unlock(d_inode(root));
}
@@ -386,8 +397,6 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
- pstore_sb = sb;
-
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
@@ -408,6 +417,10 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
if (!sb->s_root)
return -ENOMEM;
+ mutex_lock(&pstore_sb_lock);
+ pstore_sb = sb;
+ mutex_unlock(&pstore_sb_lock);
+
pstore_get_records(0);
return 0;
@@ -421,9 +434,17 @@ static struct dentry *pstore_mount(struct file_system_type *fs_type,
static void pstore_kill_sb(struct super_block *sb)
{
+ mutex_lock(&pstore_sb_lock);
+ WARN_ON(pstore_sb != sb);
+
kill_litter_super(sb);
pstore_sb = NULL;
+
+ mutex_lock(&records_list_lock);
INIT_LIST_HEAD(&records_list);
+ mutex_unlock(&records_list_lock);
+
+ mutex_unlock(&pstore_sb_lock);
}
static struct file_system_type pstore_fs_type = {
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index 7062ea4bc57c..fe5f7ef7323f 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -33,7 +33,6 @@ extern void pstore_get_backend_records(struct pstore_info *psi,
struct dentry *root, int quiet);
extern int pstore_mkfile(struct dentry *root,
struct pstore_record *record);
-extern bool pstore_is_mounted(void);
extern void pstore_record_init(struct pstore_record *record,
struct pstore_info *psi);
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 03bc847a6951..55f46837a7f4 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -460,7 +460,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
}
ret = psinfo->write(&record);
- if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
+ if (ret == 0 && reason == KMSG_DUMP_OOPS)
pstore_new_entry = 1;
total += record.size;
@@ -594,8 +594,7 @@ int pstore_register(struct pstore_info *psi)
if (psi->flags & PSTORE_FLAGS_DMESG)
allocate_buf_for_compression();
- if (pstore_is_mounted())
- pstore_get_records(0);
+ pstore_get_records(0);
if (psi->flags & PSTORE_FLAGS_DMESG)
pstore_register_kmsg();
--
2.20.1
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