Fix race between proc_readdir and remove_proc_entry
Fix the following race:
proc_readdir remove_proc_entry
============ =================
spin_lock(&proc_subdir_lock);
[choose PDE to start filldir from]
spin_unlock(&proc_subdir_lock);
spin_lock(&proc_subdir_lock);
[find PDE]
[free PDE, refcount is 0]
spin_unlock(&proc_subdir_lock);
/* boom */
if (filldir(dirent, de->name, ...
[de_put on error path --adobriyan]
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 22a08ff..8a40e15 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -478,14 +478,21 @@
}
do {
+ struct proc_dir_entry *next;
+
/* filldir passes info to user space */
+ de_get(de);
spin_unlock(&proc_subdir_lock);
if (filldir(dirent, de->name, de->namelen, filp->f_pos,
- de->low_ino, de->mode >> 12) < 0)
+ de->low_ino, de->mode >> 12) < 0) {
+ de_put(de);
goto out;
+ }
spin_lock(&proc_subdir_lock);
filp->f_pos++;
- de = de->next;
+ next = de->next;
+ de_put(de);
+ de = next;
} while (de);
spin_unlock(&proc_subdir_lock);
}