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Message-ID: <20110905185358.GA2103@albatros> Date: Mon, 5 Sep 2011 22:53:58 +0400 From: Vasiliy Kulikov <segoon@...nwall.com> To: Cyrill Gorcunov <gorcunov@...il.com>, Andrew Morton <akpm@...ux-foundation.org> Cc: "Kirill A. Shutemov" <kirill@...temov.name>, containers@...ts.osdl.org, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, Nathan Lynch <ntl@...ox.com>, kernel-hardening@...ts.openwall.com, Oren Laadan <orenl@...columbia.edu>, Daniel Lezcano <dlezcano@...ibm.com>, Glauber Costa <glommer@...allels.com>, James Bottomley <jbottomley@...allels.com>, Tejun Heo <tj@...nel.org>, Alexey Dobriyan <adobriyan@...il.com>, Al Viro <viro@...IV.linux.org.uk>, Pavel Emelyanov <xemul@...allels.com> Subject: Re: [patch 2/2] fs, proc: Introduce the /proc/<pid>/map_files/ directory v6 On Fri, Sep 02, 2011 at 20:37 +0400, Vasiliy Kulikov wrote: > On Thu, Sep 01, 2011 at 12:05 +0400, Cyrill Gorcunov wrote: > > ... > > > > +/* > > > > + * NOTE: The getattr/setattr for both /proc/$pid/map_files and > > > > + * /proc/$pid/fd seems to have share the code, so need to be > > > > + * unified and code duplication eliminated! > > > > > > Why not do this now? > > > > There are a couple of reasons. Yesterday I was talking to > > Vasiliy Kulikov about this snippet, so he seems about to send > > you patches related to /proc/$pid/fd update, and after those > > patches will be merged we are to drop code duplication. > > Vasiliy, what the status of the update? > > It looks like protecting directories with sensible contents is a nasty > thing. The problem here is that if the dentry is present in the cache, > ->lookup() is not called at all and the permissions can be checked in > fop/dop/iop specific handler (getattr(), readlink(), etc.). However, it > would be much simplier to hook ->lookup() only. Otherwise, we have to > define procfs handlers for all operations, which don't call > ->d_revalidate(). > > Is it possible to disable caching dentry for specific files? It is not > performace critical thing in fd and map_files and it would much simplify > the task. Creating handlers for all these op handler bloats procfs. Looks like the following patch solves the problem. Tested on stat() and link(). diff --git a/fs/proc/base.c b/fs/proc/base.c index d44c701..219588b 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1665,46 +1665,12 @@ out: return error; } -static int proc_pid_fd_link_getattr(struct vfsmount *mnt, struct dentry *dentry, - struct kstat *stat) -{ - struct inode *inode = dentry->d_inode; - struct task_struct *task = get_proc_task(inode); - int rc; - - if (task == NULL) - return -ESRCH; - - rc = -EACCES; - if (lock_trace(task)) - goto out_task; - - generic_fillattr(inode, stat); - unlock_trace(task); - rc = 0; -out_task: - put_task_struct(task); - return rc; -} - static const struct inode_operations proc_pid_link_inode_operations = { .readlink = proc_pid_readlink, .follow_link = proc_pid_follow_link, .setattr = proc_setattr, }; -static const struct inode_operations proc_fdinfo_link_inode_operations = { - .setattr = proc_setattr, - .getattr = proc_pid_fd_link_getattr, -}; - -static const struct inode_operations proc_fd_link_inode_operations = { - .readlink = proc_pid_readlink, - .follow_link = proc_pid_follow_link, - .setattr = proc_setattr, - .getattr = proc_pid_fd_link_getattr, -}; - /* building an inode */ @@ -2044,9 +2010,18 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd) return 0; } +static int pid_no_revalidate(struct dentry *dentry, struct nameidata *nd) +{ + if (nd && nd->flags & LOOKUP_RCU) + return -ECHILD; + + d_drop(dentry); + return 0; +} + static const struct dentry_operations tid_fd_dentry_operations = { - .d_revalidate = tid_fd_revalidate, + .d_revalidate = pid_no_revalidate, .d_delete = pid_delete_dentry, }; @@ -2085,7 +2060,7 @@ static struct dentry *proc_fd_instantiate(struct inode *dir, spin_unlock(&files->file_lock); put_files_struct(files); - inode->i_op = &proc_fd_link_inode_operations; + inode->i_op = &proc_pid_link_inode_operations; inode->i_size = 64; ei->op.proc_get_link = proc_fd_link; d_set_d_op(dentry, &tid_fd_dentry_operations); @@ -2267,7 +2242,6 @@ static struct dentry *proc_fdinfo_instantiate(struct inode *dir, ei->fd = fd; inode->i_mode = S_IFREG | S_IRUSR; inode->i_fop = &proc_fdinfo_file_operations; - inode->i_op = &proc_fdinfo_link_inode_operations; d_set_d_op(dentry, &tid_fd_dentry_operations); d_add(dentry, inode); /* Close the race of the process dying before we return the dentry */ -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
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