anonfd: Allow making anon files read-only

It seems a couple places such as arch/ia64/kernel/perfmon.c and
drivers/infiniband/core/uverbs_main.c could use anon_inode_getfile()
instead of a private pseudo-fs + alloc_file(), if only there were a way
to get a read-only file.  So provide this by having anon_inode_getfile()
create a read-only file if we pass O_RDONLY in flags.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/signalfd.c b/fs/signalfd.c
index b07565c94386..1dabe4ee02fe 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -236,7 +236,7 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
                  * anon_inode_getfd() will install the fd.
                  */
                 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
-                                       flags & (O_CLOEXEC | O_NONBLOCK));
+                                       O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK)));
                 if (ufd < 0)
                         kfree(ctx);
         } else {