From 27e5041a87e8af2d0b6452dffe053d0253e914cc Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Mon, 4 May 2020 19:43:41 -0700 Subject: 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. Link: https://lore.kernel.org/lkml/20200506152114.50375-9-keescook@chromium.org/ Signed-off-by: Kees Cook --- fs/pstore/inode.c | 65 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 43 insertions(+), 22 deletions(-) (limited to 'fs/pstore/inode.c') diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c index 5f08b21b7a46..0e76e12fa6d1 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) +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 @@ fail_private: free_pstore_private(private); fail_inode: iput(inode); - fail: + mutex_unlock(&records_list_lock); return rc; } @@ -369,16 +383,13 @@ fail: */ 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 = { -- cgit v1.2.3