[RFC][PATCH 4/4] anon_inode fcntl() checks: report failure for fcntl(F_SETFL) on eventfd

[Matt Helsley]

Report failure when userspace attempts to set unsupported flags
on eventfd files with fcntl().

Signed-off-by: Matt Helsley <matthltc@xxxxxxxxxx>
Cc: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
---
 fs/eventfd.c |   15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index 7758cc3..8976079 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -287,7 +287,19 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
 	return res;
 }
 
+static int eventfd_check_flags(int flags)
+{
+	/* Check the EFD_* constants for consistency.  */
+	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
+	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
+
+	if (flags & ~EFD_SHARED_FCNTL_FLAGS)
+		return -EINVAL;
+	return 0;
+}
+
 static const struct file_operations eventfd_fops = {
+	.check_flags    = eventfd_check_flags,
 	.release	= eventfd_release,
 	.poll		= eventfd_poll,
 	.read		= eventfd_read,
@@ -381,9 +393,6 @@ struct file *eventfd_file_create(unsigned int count, int flags)
 	struct file *file;
 	struct eventfd_ctx *ctx;
 
-	/* Check the EFD_* constants for consistency.  */
-	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
-	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
 
 	if (flags & ~EFD_FLAGS_SET)
 		return ERR_PTR(-EINVAL);
-- 
1.6.3.3

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