linux-kernel - [RFC][PATCH] fs/signalfd.c: Fix inconsistent return codes for signalfd4

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Date:   Sat, 25 Apr 2020 23:42:47 +0200
From:   Helge Deller <deller@....de>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Laurent Vivier <laurent@...ier.eu>
Subject: [RFC][PATCH] fs/signalfd.c: Fix inconsistent return codes for
 signalfd4

The kernel provides a native and a compat implementation for the
signalfd4() syscall.

While looking into the qemu user emulation code, I noticed that in the
kernel compat case, EFAULT is returned if the given user mask can't be
accessed, while the native path returns EINVAL on such failure.

For the sake of consistency, this patch adjusts the native path to
return the same error code (EFAULT) as the compat case.

Signed-off-by: Helge Deller <deller@....de>

diff --git a/fs/signalfd.c b/fs/signalfd.c
index 44b6845b071c..5b78719be445 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -314,9 +314,10 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
 {
 	sigset_t mask;

-	if (sizemask != sizeof(sigset_t) ||
-	    copy_from_user(&mask, user_mask, sizeof(mask)))
+	if (sizemask != sizeof(sigset_t))
 		return -EINVAL;
+	if (copy_from_user(&mask, user_mask, sizeof(mask)))
+		return -EFAULT;
 	return do_signalfd4(ufd, &mask, flags);
 }

@@ -325,9 +326,10 @@ SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask,
 {
 	sigset_t mask;

-	if (sizemask != sizeof(sigset_t) ||
-	    copy_from_user(&mask, user_mask, sizeof(mask)))
+	if (sizemask != sizeof(sigset_t))
 		return -EINVAL;
+	if (copy_from_user(&mask, user_mask, sizeof(mask)))
+		return -EFAULT;
 	return do_signalfd4(ufd, &mask, 0);
 }