diff options
Diffstat (limited to 'fs/ext4/dir.c')
| -rw-r--r-- | fs/ext4/dir.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index 2743c6f8a457..0589e914663f 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -677,6 +677,7 @@ static int ext4_d_compare(const struct dentry *dentry, unsigned int len, struct qstr qstr = {.name = str, .len = len }; const struct dentry *parent = READ_ONCE(dentry->d_parent); const struct inode *inode = READ_ONCE(parent->d_inode); + char strbuf[DNAME_INLINE_LEN]; if (!inode || !IS_CASEFOLDED(inode) || !EXT4_SB(inode->i_sb)->s_encoding) { @@ -685,6 +686,21 @@ static int ext4_d_compare(const struct dentry *dentry, unsigned int len, return memcmp(str, name->name, len); } + /* + * If the dentry name is stored in-line, then it may be concurrently + * modified by a rename. If this happens, the VFS will eventually retry + * the lookup, so it doesn't matter what ->d_compare() returns. + * However, it's unsafe to call utf8_strncasecmp() with an unstable + * string. Therefore, we have to copy the name into a temporary buffer. + */ + if (len <= DNAME_INLINE_LEN - 1) { + memcpy(strbuf, str, len); + strbuf[len] = 0; + qstr.name = strbuf; + /* prevent compiler from optimizing out the temporary buffer */ + barrier(); + } + return ext4_ci_compare(inode, name, &qstr, false); } |