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authorEric Biggers <ebiggers@google.com>2020-01-23 20:15:49 -0800
committerJaegeuk Kim <jaegeuk@kernel.org>2020-01-24 10:04:09 -0800
commit80f2388afa6ef985f9c5c228e36705c4d4db4756 (patch)
tree1e895395075dd074b38d1f1387a2e40c8301f0db /fs/f2fs/dir.c
parent5515eae647426169e4b7969271fb207881eba7f6 (diff)
f2fs: fix race conditions in ->d_compare() and ->d_hash()
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>
Diffstat (limited to 'fs/f2fs/dir.c')
-rw-r--r--fs/f2fs/dir.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index aea9e2806144..d7c9a2cda489 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -1083,24 +1083,27 @@ 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);