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authorAl Viro <viro@zeniv.linux.org.uk>2011-07-16 23:37:20 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2011-07-16 23:37:20 -0400
commitdc137bf553dbb6855bd7efc34fedcd03102455f7 (patch)
treeab1fefc7da26bb86655a28651c4eafb56d741ea1
parent3110df800c4de2724624d46e6bed27efc5e9a707 (diff)
cifs: build_path_from_dentry() race fix
deal with d_move() races properly; rename_lock read-retry loop, rcu_read_lock() held while walking to root, d_lock held over subtraction from namelen and copying the component to stabilize ->d_name. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/cifs/dir.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 81914df47ef1..fa8c21d913bc 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -55,6 +55,7 @@ build_path_from_dentry(struct dentry *direntry)
char dirsep;
struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb);
struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+ unsigned seq;
if (direntry == NULL)
return NULL; /* not much we can do if dentry is freed and
@@ -68,22 +69,29 @@ build_path_from_dentry(struct dentry *direntry)
dfsplen = 0;
cifs_bp_rename_retry:
namelen = dfsplen;
+ seq = read_seqbegin(&rename_lock);
+ rcu_read_lock();
for (temp = direntry; !IS_ROOT(temp);) {
namelen += (1 + temp->d_name.len);
temp = temp->d_parent;
if (temp == NULL) {
cERROR(1, "corrupt dentry");
+ rcu_read_unlock();
return NULL;
}
}
+ rcu_read_unlock();
full_path = kmalloc(namelen+1, GFP_KERNEL);
if (full_path == NULL)
return full_path;
full_path[namelen] = 0; /* trailing null */
+ rcu_read_lock();
for (temp = direntry; !IS_ROOT(temp);) {
+ spin_lock(&temp->d_lock);
namelen -= 1 + temp->d_name.len;
if (namelen < 0) {
+ spin_unlock(&temp->d_lock);
break;
} else {
full_path[namelen] = dirsep;
@@ -91,14 +99,17 @@ cifs_bp_rename_retry:
temp->d_name.len);
cFYI(0, "name: %s", full_path + namelen);
}
+ spin_unlock(&temp->d_lock);
temp = temp->d_parent;
if (temp == NULL) {
cERROR(1, "corrupt dentry");
+ rcu_read_unlock();
kfree(full_path);
return NULL;
}
}
- if (namelen != dfsplen) {
+ rcu_read_unlock();
+ if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) {
cERROR(1, "did not end path lookup where expected namelen is %d",
namelen);
/* presumably this is only possible if racing with a rename