summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorEric Paris <eparis@redhat.com>2011-04-05 17:20:50 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-04-05 15:27:14 -0700
commitd0de4dc584ec6aa3b26fffea320a8457827768fc (patch)
tree6895419a694ba323c6b18cdb6aa2714892b6f481
parent623dda65b6f71e6474f3f156dbed2acf6ff43584 (diff)
downloadconfigs-d0de4dc584ec6aa3b26fffea320a8457827768fc.tar.gz
inotify: fix double free/corruption of stuct user
On an error path in inotify_init1 a normal user can trigger a double free of struct user. This is a regression introduced by a2ae4cc9a16e ("inotify: stop kernel memory leak on file creation failure"). We fix this by making sure that if a group exists the user reference is dropped when the group is cleaned up. We should not explictly drop the reference on error and also drop the reference when the group is cleaned up. The new lifetime rules are that an inotify group lives from inotify_new_group to the last fsnotify_put_group. Since the struct user and inotify_devs are directly tied to this lifetime they are only changed/updated in those two locations. We get rid of all special casing of struct user or user->inotify_devs. Signed-off-by: Eric Paris <eparis@redhat.com> Cc: stable@kernel.org (2.6.37 and up) Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/notify/inotify/inotify_fsnotify.c1
-rw-r--r--fs/notify/inotify/inotify_user.c39
2 files changed, 14 insertions, 26 deletions
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index a91b69a6a29..0348d0c8f65 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -198,6 +198,7 @@ static void inotify_free_group_priv(struct fsnotify_group *group)
idr_for_each(&group->inotify_data.idr, idr_callback, group);
idr_remove_all(&group->inotify_data.idr);
idr_destroy(&group->inotify_data.idr);
+ atomic_dec(&group->inotify_data.user->inotify_devs);
free_uid(group->inotify_data.user);
}
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index bd46e7c8a0e..8445fbc8985 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -290,7 +290,6 @@ static int inotify_fasync(int fd, struct file *file, int on)
static int inotify_release(struct inode *ignored, struct file *file)
{
struct fsnotify_group *group = file->private_data;
- struct user_struct *user = group->inotify_data.user;
pr_debug("%s: group=%p\n", __func__, group);
@@ -299,8 +298,6 @@ static int inotify_release(struct inode *ignored, struct file *file)
/* free this group, matching get was inotify_init->fsnotify_obtain_group */
fsnotify_put_group(group);
- atomic_dec(&user->inotify_devs);
-
return 0;
}
@@ -697,7 +694,7 @@ retry:
return ret;
}
-static struct fsnotify_group *inotify_new_group(struct user_struct *user, unsigned int max_events)
+static struct fsnotify_group *inotify_new_group(unsigned int max_events)
{
struct fsnotify_group *group;
@@ -710,8 +707,14 @@ static struct fsnotify_group *inotify_new_group(struct user_struct *user, unsign
spin_lock_init(&group->inotify_data.idr_lock);
idr_init(&group->inotify_data.idr);
group->inotify_data.last_wd = 0;
- group->inotify_data.user = user;
group->inotify_data.fa = NULL;
+ group->inotify_data.user = get_current_user();
+
+ if (atomic_inc_return(&group->inotify_data.user->inotify_devs) >
+ inotify_max_user_instances) {
+ fsnotify_put_group(group);
+ return ERR_PTR(-EMFILE);
+ }
return group;
}
@@ -721,7 +724,6 @@ static struct fsnotify_group *inotify_new_group(struct user_struct *user, unsign
SYSCALL_DEFINE1(inotify_init1, int, flags)
{
struct fsnotify_group *group;
- struct user_struct *user;
int ret;
/* Check the IN_* constants for consistency. */
@@ -731,31 +733,16 @@ SYSCALL_DEFINE1(inotify_init1, int, flags)
if (flags & ~(IN_CLOEXEC | IN_NONBLOCK))
return -EINVAL;
- user = get_current_user();
- if (unlikely(atomic_read(&user->inotify_devs) >=
- inotify_max_user_instances)) {
- ret = -EMFILE;
- goto out_free_uid;
- }
-
/* fsnotify_obtain_group took a reference to group, we put this when we kill the file in the end */
- group = inotify_new_group(user, inotify_max_queued_events);
- if (IS_ERR(group)) {
- ret = PTR_ERR(group);
- goto out_free_uid;
- }
-
- atomic_inc(&user->inotify_devs);
+ group = inotify_new_group(inotify_max_queued_events);
+ if (IS_ERR(group))
+ return PTR_ERR(group);
ret = anon_inode_getfd("inotify", &inotify_fops, group,
O_RDONLY | flags);
- if (ret >= 0)
- return ret;
+ if (ret < 0)
+ fsnotify_put_group(group);
- fsnotify_put_group(group);
- atomic_dec(&user->inotify_devs);
-out_free_uid:
- free_uid(user);
return ret;
}