This is a note to let you know that I've just added the patch titled
vfs,proc: guarantee unique inodes in /proc
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vfs-proc-guarantee-unique-inodes-in-proc.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4c239ba63bccc9d0f2829815a31f7972e925ab7f Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 22 Mar 2013 11:44:04 -0700
Subject: vfs,proc: guarantee unique inodes in /proc
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
commit 51f0885e5415b4cc6535e9cdcc5145bfbc134353 upstream.
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@xxxxxxxxxx>
Analyzed-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- Never drop the pde reference in proc_get_inode(), as callers only
expect this when we return an existing inode, and we never do that now]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Rui Xiang <rui.xiang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/proc/inode.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -443,12 +443,10 @@ static const struct file_operations proc
struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
{
- struct inode * inode;
+ struct inode *inode = new_inode_pseudo(sb);
- inode = iget_locked(sb, de->low_ino);
- if (!inode)
- return NULL;
- if (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)->fd = 0;
PROC_I(inode)->pde = de;
@@ -477,9 +475,7 @@ struct inode *proc_get_inode(struct supe
inode->i_fop = de->proc_fops;
}
}
- unlock_new_inode(inode);
- } else
- pde_put(de);
+ }
return inode;
}
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-3.4/vfs-proc-guarantee-unique-inodes-in-proc.patch
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