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authorEric W. Biederman <ebiederm@xmission.com>2006-06-26 00:25:57 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 09:58:26 -0700
commit5b0c1dd38b66e2dd0cf655aa845e341b50b93ddd (patch)
treee8d3341591958d9c3e11400a2f16287a6dd00c46 /fs/proc
parent13b41b09491e5d75e8027dca1ee78f5e073bc4c0 (diff)
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[PATCH] proc: optimize proc_check_dentry_visible
The code doesn't need to sleep to when making this check so I can just do the comparison and not worry about the reference counts. TODO: While looking at this I realized that my original cleanup did not push the permission check far enough down into the stack. The call of proc_check_dentry_visible needs to move out of the generic proc readlink/follow link code and into the individual get_link instances. Otherwise the shared resources checks are not quite correct (shared files_struct does not require a shared fs_struct), and there are races with unshare. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/base.c29
1 files changed, 16 insertions, 13 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c7f85544157..f0db7f616ac 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1074,24 +1074,27 @@ static int proc_check_dentry_visible(struct inode *inode,
* namespace, or are simply process local (like pipes).
*/
struct task_struct *task;
- struct files_struct *task_files, *files;
int error = -EACCES;
/* See if the the two tasks share a commone set of
* file descriptors. If so everything is visible.
*/
- task = get_proc_task(inode);
- if (!task)
- goto out;
- files = get_files_struct(current);
- task_files = get_files_struct(task);
- if (files && task_files && (files == task_files))
- error = 0;
- if (task_files)
- put_files_struct(task_files);
- if (files)
- put_files_struct(files);
- put_task_struct(task);
+ rcu_read_lock();
+ task = tref_task(proc_tref(inode));
+ if (task) {
+ struct files_struct *task_files, *files;
+ /* This test answeres the question:
+ * Is there a point in time since we looked up the
+ * file descriptor where the two tasks share the
+ * same files struct?
+ */
+ rmb();
+ files = current->files;
+ task_files = task->files;
+ if (files && (files == task_files))
+ error = 0;
+ }
+ rcu_read_unlock();
if (!error)
goto out;