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pstore: Add locking around superblock changes

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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.

Link: https://lore.kernel.org/lkml/20200506152114.50375-9-keescook@chromium.org/
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-05-04 19:43:41 -07:00
parent 7a0ad54684
commit 27e5041a87
3 changed files with 45 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
fs/pstore/inode.c
View File

@ -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)
static 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 = {

1
fs/pstore/internal.h
View File

@ -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);

5
fs/pstore/platform.c
View File

@ -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;
@ -592,8 +592,7 @@ 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();