[PATCH] dcache: trivial comment fix

[PATCH] dcache: trivial comment fix

[J. Bruce Fields]

From: J. Bruce Fields <bfields@citi.umich.edu>

As it stands this comment is confusing, and not quite grammatical.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
---
 fs/dcache.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 7da0cf5..5663a31 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1514,8 +1514,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
  * This forceful removal will result in ugly /proc output if
  * somebody holds a file open that got deleted due to a rename.
  * We could be nicer about the deleted file, and let it show
- * up under the name it got deleted rather than the name that
- * deleted it.
+ * up under the name it had before it was deleted rather than
+ * the original name of the file that was moved on top of it.
  */
  
 /*
-- 
1.5.3.4.208.gc990

[PATCH] dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

[J. Bruce Fields]

From: J. Bruce Fields <bfields@citi.umich.edu>

Well, it's not especially important that target->d_iname get the
contents of dentry->d_iname, but it's important that it get initialized
with *something*, otherwise we're just exposing some random piece of
memory to anyone who reads the link at /proc/<pid>/fd/<fd> for the
deleted file, when it's still held open by someone.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
---
 fs/dcache.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

(Am I missing something?  I've also run a test program that copies a
short (<36 character) name ontop of a long (>=36 character) name and see
that the first time I run it, without this patch, I get unpredicatable
results out of /proc/<pid>/fd/<fd>.)

diff --git a/fs/dcache.c b/fs/dcache.c
index 5663a31..24252fc 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1483,6 +1483,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
 			 * dentry:internal, target:external.  Steal target's
 			 * storage and make target internal.
 			 */
+			memcpy(target->d_iname, dentry->d_name.name,
+					dentry->d_name.len + 1);
 			dentry->d_name.name = target->d_name.name;
 			target->d_name.name = target->d_iname;
 		}
-- 
1.5.3.4.208.gc990

Re: [PATCH] dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

[Andrew Morton]

On Tue, 16 Oct 2007 15:35:57 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> From: J. Bruce Fields <bfields@citi.umich.edu>
> 
> Well, it's not especially important that target->d_iname get the
> contents of dentry->d_iname, but it's important that it get initialized
> with *something*, otherwise we're just exposing some random piece of
> memory to anyone who reads the link at /proc/<pid>/fd/<fd> for the
> deleted file, when it's still held open by someone.
> 

hm, that was tricky.

> ---
>  fs/dcache.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> (Am I missing something?  I've also run a test program that copies a
> short (<36 character) name ontop of a long (>=36 character) name and see
> that the first time I run it, without this patch, I get unpredicatable
> results out of /proc/<pid>/fd/<fd>.)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 5663a31..24252fc 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1483,6 +1483,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
>  			 * dentry:internal, target:external.  Steal target's
>  			 * storage and make target internal.
>  			 */
> +			memcpy(target->d_iname, dentry->d_name.name,
> +					dentry->d_name.len + 1);
>  			dentry->d_name.name = target->d_name.name;
>  			target->d_name.name = target->d_iname;
>  		}

Or we could just stick a \0 in there.

Or perhaps we should set it to "(deleted file)"?

Re: [PATCH] dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

[J. Bruce Fields]

Sorry for the delayed response:

On Wed, Oct 17, 2007 at 03:32:01PM -0700, Andrew Morton wrote:
> On Tue, 16 Oct 2007 15:35:57 -0400
> "J. Bruce Fields" <bfields@fieldses.org> wrote:
> 
> > From: J. Bruce Fields <bfields@citi.umich.edu>
> > 
> > Well, it's not especially important that target->d_iname get the
> > contents of dentry->d_iname, but it's important that it get initialized
> > with *something*, otherwise we're just exposing some random piece of
> > memory to anyone who reads the link at /proc/<pid>/fd/<fd> for the
> > deleted file, when it's still held open by someone.
> > 
> 
> hm, that was tricky.
> 
> > ---
> >  fs/dcache.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > (Am I missing something?  I've also run a test program that copies a
> > short (<36 character) name ontop of a long (>=36 character) name and see
> > that the first time I run it, without this patch, I get unpredicatable
> > results out of /proc/<pid>/fd/<fd>.)
> > 
> > diff --git a/fs/dcache.c b/fs/dcache.c
> > index 5663a31..24252fc 100644
> > --- a/fs/dcache.c
> > +++ b/fs/dcache.c
> > @@ -1483,6 +1483,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
> >  			 * dentry:internal, target:external.  Steal target's
> >  			 * storage and make target internal.
> >  			 */
> > +			memcpy(target->d_iname, dentry->d_name.name,
> > +					dentry->d_name.len + 1);
> >  			dentry->d_name.name = target->d_name.name;
> >  			target->d_name.name = target->d_iname;
> >  		}
> 
> Or we could just stick a \0 in there.

The memcpy() makes the behavior agree with the code comments, and with
what the kernel normally otherwise does.  But, yeah, just making it a
null string would probably be reasonable too.

> Or perhaps we should set it to "(deleted file)"?

Looks like __d_path already adds a (deleted) for us, so that'de be
redundant.

--b.