vfs: fix pipe counter breakage

commit a930d8790552658140d7d0d2e316af4f0d76a512 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/pipe.c b/fs/pipe.c
index 05ed5cabd4575d6c7bea67c48dd7e382b540364e..8ca88fcba07e54c5ff3fee87e95e3d1d437c5b3d 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -859,6 +859,9 @@ 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) {