-EINVAL if no fasync op for file

PATCH In review Dmitry Antipov 2 participants 2 messages Oct 18, 2007 – Oct 26, 2007

Subsystems (2)

VFS File locking (flock() and fcntl()/lockf())

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Share & tools

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Dmitry Antipov

author

2007-10-18 09:50 UTC #0 lore raw

PATCH 1/1 -EINVAL if no fasync op for file

This patch proposes an additional error checking performed within setfl().

As a result, fcntl (fd, F_SETFL, O_ASYNC) will return -1 and set errno to -EINVAL if filp->f_op->fasync is NULL for file specified by fd. This is possible, for example, if fd is a descriptor returned by inotify_init().

Dmitry

Signed-off-by Dmitry Antipov <[email protected]>

fs/fcntl.c +3 -0

@@ -240,6 +240,9 @@
 			error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 			if (error < 0)
 				goto out;
+		} else {
+			error = -EINVAL;
+			goto out;
 		}
 	}

Andrew Morton

2007-10-26 20:25 UTC #1 lore raw

Quoted 17 lines · On Thu, 18 Oct 2007 13:35:51 +0400 Dmitry Antipov <[email protected]> wrote:

This patch proposes an additional error checking performed within setfl().
As a result, fcntl (fd, F_SETFL, O_ASYNC) will return -1 and set errno to -EINVAL if filp->f_op->fasync is NULL for file specified by fd. This is possible, for example, if fd is a descriptor returned by inotify_init().
Dmitry
[2.6.23-fcntl-fasync-check.patch text/x-patch (353B)]
Signed-off-by Dmitry Antipov <[email protected]>

fs/fcntl.c line 247

Quoted 8 lines

fs/fcntl.c +3 -0

@@ -240,6 +240,9 @@
 			error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
 			if (error < 0)
 				goto out;
+		} else {
+			error = -EINVAL;
+			goto out;
 		}
 	}

This would have made sense whent he code was originally written but it now has a (small) potential to break existing applications.

I guess if the _only_ fd's which don't implement fasync are inotify, signalfd and other such new-and-obscure things then the risk is probably acceptably low.

But is the proposed change actually very useful?