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Subject[RFC][PATCH 1/4] anon_inode fcntl() checks: report failure for fcntl(F_SETFL) on signalfd
Date
anon_inode interfaces often do not support flags that can be set
by fcntl(). Right now using fcntl() to set these flags falsely
reports success for things like O_ASYNC (yet SIGIO is not delivered).

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

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
---
fs/signalfd.c | 19 +++++++++++++------
1 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 1dabe4e..3016f3b 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -199,7 +199,19 @@ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count,
return total ? total: ret;
}

+static int signalfd_check_flags(int flags)
+{
+ /* Check the SFD_* constants for consistency. */
+ BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
+ BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
+
+ if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
+ return -EINVAL;
+ return 0;
+}
+
static const struct file_operations signalfd_fops = {
+ .check_flags = signalfd_check_flags,
.release = signalfd_release,
.poll = signalfd_poll,
.read = signalfd_read,
@@ -211,13 +223,8 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
sigset_t sigmask;
struct signalfd_ctx *ctx;

- /* Check the SFD_* constants for consistency. */
- BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
- BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
-
- if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK))
+ if (signalfd_check_flags(flags))
return -EINVAL;
-
if (sizemask != sizeof(sigset_t) ||
copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
return -EINVAL;
--
1.6.3.3


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