diff options
author | Eric Biggers <ebiggers@google.com> | 2020-01-24 07:15:49 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-11 15:35:25 +0300 |
commit | e9116299ffac758111547667f9bc8a0f284c5d93 (patch) | |
tree | 8adfc37c1f1fd8db72562937b0be7cad00fce67a /fs | |
parent | 6d722cd2e387921316ce52d1de9d4dbd88972ad8 (diff) | |
download | linux-e9116299ffac758111547667f9bc8a0f284c5d93.tar.xz |
f2fs: fix race conditions in ->d_compare() and ->d_hash()
commit 80f2388afa6ef985f9c5c228e36705c4d4db4756 upstream.
Since ->d_compare() and ->d_hash() can be called in RCU-walk mode,
->d_parent and ->d_inode can be concurrently modified, and in
particular, ->d_inode may be changed to NULL. For f2fs_d_hash() this
resulted in a reproducible NULL dereference if a lookup is done in a
directory being deleted, e.g. with:
int main()
{
if (fork()) {
for (;;) {
mkdir("subdir", 0700);
rmdir("subdir");
}
} else {
for (;;)
access("subdir/file", 0);
}
}
... or by running the 't_encrypted_d_revalidate' program from xfstests.
Both repros work in any directory on a filesystem with the encoding
feature, even if the directory doesn't actually have the casefold flag.
I couldn't reproduce a crash in f2fs_d_compare(), but it appears that a
similar crash is possible there.
Fix these bugs by reading ->d_parent and ->d_inode using READ_ONCE() and
falling back to the case sensitive behavior if the inode is NULL.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
Cc: <stable@vger.kernel.org> # v5.4+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/f2fs/dir.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 810e70c3b425..84280ad3786c 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1068,24 +1068,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { 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); - if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) { + if (!inode || !IS_CASEFOLDED(inode)) { if (len != name->len) return -1; return memcmp(str, name->name, len); } - return f2fs_ci_compare(dentry->d_parent->d_inode, name, &qstr, false); + return f2fs_ci_compare(inode, name, &qstr, false); } static int f2fs_d_hash(const struct dentry *dentry, struct qstr *str) { struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb); const struct unicode_map *um = sbi->s_encoding; + const struct inode *inode = READ_ONCE(dentry->d_inode); unsigned char *norm; int len, ret = 0; - if (!IS_CASEFOLDED(dentry->d_inode)) + if (!inode || !IS_CASEFOLDED(inode)) return 0; norm = f2fs_kmalloc(sbi, PATH_MAX, GFP_ATOMIC); |