Andrew Morton wrote:
> On Thu, 06 Dec 2007 09:21:53 +0100 Giacomo Catenazzi <[email protected]> wrote:
>
>> Andrew Morton wrote:
>>> On Mon, 3 Dec 2007 19:00:25 GMT Linux Kernel Mailing List <[email protected]> wrote:
>>>
>>>> Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
>>>> Commit: 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
>>>> Parent: e03ba84adb62fbc6049325a5bc00ef6932fa5e39
>>>> Author: Eric W. Biederman <[email protected]>
>>>> AuthorDate: Sun Dec 2 00:33:17 2007 +1100
>>>> Committer: Herbert Xu <[email protected]>
>>>> CommitDate: Sun Dec 2 00:33:17 2007 +1100
>>>>
>>>> [NETNS]: Fix /proc/net breakage
>>>>
>>>> Well I clearly goofed when I added the initial network namespace support
>>>> for /proc/net. Currently things work but there are odd details visible to
>>>> user space, even when we have a single network namespace.
>>>>
>>>> Since we do not cache proc_dir_entry dentries at the moment we can just
>>>> modify ->lookup to return a different directory inode depending on the
>>>> network namespace of the process looking at /proc/net, replacing the
>>>> current technique of using a magic and fragile follow_link method.
>>>>
>>>> To accomplish that this patch:
>>>> - introduces a shadow_proc method to allow different dentries to
>>>> be returned from proc_lookup.
>>>> - Removes the old /proc/net follow_link magic
>>>> - Fixes a weakness in our not caching of proc generic dentries.
>>>>
>>>> As shadow_proc uses a task struct to decided which dentry to return we can
>>>> go back later and fix the proc generic caching without modifying any code
>>>> that uses the shadow_proc method.
>>> This patch caused the binfmt_misc regression reported in
>>> http://bugzilla.kernel.org/show_bug.cgi?id=9504
>> This patch also doesn't allow to mount /proc/bus/usb
>>
>
> Does Denis's patch fix it?
Yes, this patch solve the problem.
Tested-by: Giacomo Catenazzi <[email protected]>
ciao
cate
>
> Thanks.
>
>
> From: "Denis V. Lunev" <[email protected]>
>
> /proc/sys/fs/binfmt_misc dentry disappeared during d_revalidate.
> d_revalidate only dentries from shadowed one and below.
> http://bugzilla.kernel.org/show_bug.cgi?id=9504
>
> Cc: Eric W. Biederman <[email protected]>
> Cc: Marcus Better <[email protected]>
> Signed-off-by: Denis V. Lunev <[email protected]>
> Cc: Marcus Better <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> ---
>
> fs/proc/generic.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff -puN fs/proc/generic.c~lost-content-of-proc-sys-fs-binfmt_misc fs/proc/generic.c
> --- a/fs/proc/generic.c~lost-content-of-proc-sys-fs-binfmt_misc
> +++ a/fs/proc/generic.c
> @@ -380,12 +380,17 @@ static int proc_revalidate_dentry(struct
> return 0;
> }
>
> -static struct dentry_operations proc_dentry_operations =
> +static struct dentry_operations proc_dentry_shadow_operations =
> {
> .d_delete = proc_delete_dentry,
> .d_revalidate = proc_revalidate_dentry,
> };
>
> +static struct dentry_operations proc_dentry_operations =
> +{
> + .d_delete = proc_delete_dentry,
> +};
> +
> /*
> * Don't create negative dentries here, return -ENOENT by hand
> * instead.
> @@ -394,6 +399,7 @@ struct dentry *proc_lookup(struct inode
> {
> struct inode *inode = NULL;
> struct proc_dir_entry * de;
> + int use_shadow = 0;
> int error = -ENOENT;
>
> lock_kernel();
> @@ -406,8 +412,10 @@ struct dentry *proc_lookup(struct inode
> if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
> unsigned int ino;
>
> - if (de->shadow_proc)
> + if (de->shadow_proc) {
> de = de->shadow_proc(current, de);
> + use_shadow = 1;
> + }
> ino = de->low_ino;
> de_get(de);
> spin_unlock(&proc_subdir_lock);
> @@ -423,6 +431,8 @@ struct dentry *proc_lookup(struct inode
>
> if (inode) {
> dentry->d_op = &proc_dentry_operations;
> + dentry->d_op = use_shadow ?
> + &proc_dentry_shadow_operations : dentry->d_parent->d_op;
> d_add(dentry, inode);
> return NULL;
> }
> _
>
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