diff options
| author | Cong Wang <xiyou.wangcong@gmail.com> | 2017-04-19 15:11:00 -0700 |
|---|---|---|
| committer | Sasha Levin <alexander.levin@microsoft.com> | 2018-02-28 22:09:51 -0500 |
| commit | 2ce8a62d862e3bcd16d12d6d7d71c0a343f4f99a (patch) | |
| tree | 1a5a7fb69b73a5be55839207cb76c5a84b6df071 /fs | |
| parent | ee3e3013bda6fdf2b88fb98068c812fffb36d0ad (diff) | |
nsfs: mark dentry with DCACHE_RCUACCESS
[ Upstream commit 073c516ff73557a8f7315066856c04b50383ac34 ]
Andrey reported a use-after-free in __ns_get_path():
spin_lock include/linux/spinlock.h:299 [inline]
lockref_get_not_dead+0x19/0x80 lib/lockref.c:179
__ns_get_path+0x197/0x860 fs/nsfs.c:66
open_related_ns+0xda/0x200 fs/nsfs.c:143
sock_ioctl+0x39d/0x440 net/socket.c:1001
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
We are under rcu read lock protection at that point:
rcu_read_lock();
d = atomic_long_read(&ns->stashed);
if (!d)
goto slow;
dentry = (struct dentry *)d;
if (!lockref_get_not_dead(&dentry->d_lockref))
goto slow;
rcu_read_unlock();
but don't use a proper RCU API on the free path, therefore a parallel
__d_free() could free it at the same time. We need to mark the stashed
dentry with DCACHE_RCUACCESS so that __d_free() will be called after all
readers leave RCU.
Fixes: e149ed2b805f ("take the targets of /proc/*/ns/* symlinks to separate fs")
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/nsfs.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/nsfs.c b/fs/nsfs.c index 99521e7c492b..845f29e15ac9 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -94,6 +94,7 @@ slow: return ERR_PTR(-ENOMEM); } d_instantiate(dentry, inode); + dentry->d_flags |= DCACHE_RCUACCESS; dentry->d_fsdata = (void *)ns_ops; d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); if (d) { |