path: root/fs
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2013-03-22 11:44:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-03-22 11:44:04 -0700
commit51f0885e5415b4cc6535e9cdcc5145bfbc134353 (patch)
tree02f31672fe288448abf0b3e1d13fbc8a77a83854 /fs
parent9217cbb8df31c10efc96362227b2ebdbb9fe996c (diff)
vfs,proc: guarantee unique inodes in /proc
Dave Jones found another /proc issue with his Trinity tool: thanks to the namespace model, we can have multiple /proc dentries that point to the same inode, aliasing directories in /proc/<pid>/net/ for example. This ends up being a total disaster, because it acts like hardlinked directories, and causes locking problems. We rely on the topological sort of the inodes pointed to by dentries, and if we have aliased directories, that odering becomes unreliable. In short: don't do this. Multiple dentries with the same (directory) inode is just a bad idea, and the namespace code should never have exposed things this way. But we're kind of stuck with it. This solves things by just always allocating a new inode during /proc dentry lookup, instead of using "iget_locked()" to look up existing inodes by superblock and number. That actually simplies the code a bit, at the cost of potentially doing more inode [de]allocations. That said, the inode lookup wasn't free either (and did a lot of locking of inodes), so it is probably not that noticeable. We could easily keep the old lookup model for non-directory entries, but rather than try to be excessively clever this just implements the minimal and simplest workaround for the problem. Reported-and-tested-by: Dave Jones <davej@redhat.com> Analyzed-by: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index a86aebc9ba7..869116c2afb 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -446,9 +446,10 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
- struct inode *inode = iget_locked(sb, de->low_ino);
+ struct inode *inode = new_inode_pseudo(sb);
- if (inode && (inode->i_state & I_NEW)) {
+ if (inode) {
+ inode->i_ino = de->low_ino;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
PROC_I(inode)->pde = de;
@@ -476,7 +477,6 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
inode->i_fop = de->proc_fops;
- unlock_new_inode(inode);
} else
return inode;