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| author | Sishuai Gong <sishuai@purdue.edu> | 2021-08-25 08:52:20 +0300 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2021-08-25 08:58:49 +0300 |
| commit | c42dd069be8dfc9b2239a5c89e73bbd08ab35de0 (patch) | |
| tree | e537efef13add0360bd77adb2818a56a318eea42 /fs/configfs | |
| parent | d07f132a225c013e59aa77f514ad9211ecab82ee (diff) | |
| download | linux-c42dd069be8dfc9b2239a5c89e73bbd08ab35de0.tar.xz | |
configfs: fix a race in configfs_lookup()
When configfs_lookup() is executing list_for_each_entry(),
it is possible that configfs_dir_lseek() is calling list_del().
Some unfortunate interleavings of them can cause a kernel NULL
pointer dereference error
Thread 1 Thread 2
//configfs_dir_lseek() //configfs_lookup()
list_del(&cursor->s_sibling);
list_for_each_entry(sd, ...)
Fix this by grabbing configfs_dirent_lock in configfs_lookup()
while iterating ->s_children.
Signed-off-by: Sishuai Gong <sishuai@purdue.edu>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/configfs')
| -rw-r--r-- | fs/configfs/dir.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index fc20bd8a6337..1466b5d01cbb 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -439,13 +439,13 @@ static struct dentry * configfs_lookup(struct inode *dir, if (!configfs_dirent_is_ready(parent_sd)) return ERR_PTR(-ENOENT); + spin_lock(&configfs_dirent_lock); list_for_each_entry(sd, &parent_sd->s_children, s_sibling) { if ((sd->s_type & CONFIGFS_NOT_PINNED) && !strcmp(configfs_get_name(sd), dentry->d_name.name)) { struct configfs_attribute *attr = sd->s_element; umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG; - spin_lock(&configfs_dirent_lock); dentry->d_fsdata = configfs_get(sd); sd->s_dentry = dentry; spin_unlock(&configfs_dirent_lock); @@ -462,10 +462,11 @@ static struct dentry * configfs_lookup(struct inode *dir, inode->i_size = PAGE_SIZE; inode->i_fop = &configfs_file_operations; } - break; + goto done; } } - + spin_unlock(&configfs_dirent_lock); +done: d_add(dentry, inode); return NULL; } |