vfs: fix pipe counter breakage

If you open a pipe for neither read nor write, the pipe code will not
add any usage counters to the pipe, causing the 'struct pipe_inode_info"
to be potentially released early.

That doesn't normally matter, since you cannot actually use the pipe,
but the pipe release code - particularly fasync handling - still expects
the actual pipe infrastructure to all be there.  And rather than adding
NULL pointer checks, let's just disallow this case, the same way we
already do for the named pipe ("fifo") case.

This is ancient going back to pre-2.4 days, and until trinity, nobody
naver noticed.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/pipe.c b/fs/pipe.c
index 64a494cef0a00be57d0800637b71caf2537c2694..2234f3f61f8d8fbc6a1f77dbaae6412130b8a5d4 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -863,6 +863,9 @@ pipe_rdwr_open(struct inode *inode, struct file *filp)
 {
        int ret = -ENOENT;
 
+       if (!(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
+               return -EINVAL;
+
        mutex_lock(&inode->i_mutex);
 
        if (inode->i_pipe) {