Patch "selinux: improve error checking in sel_write_load()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    selinux: improve error checking in sel_write_load()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selinux-improve-error-checking-in-sel_write_load.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9b96c19a58b0c1a1bce6877617cdad028fd435bc
Author: Paul Moore <paul@xxxxxxxxxxxxxx>
Date:   Fri Oct 25 11:21:18 2024 -0300

    selinux: improve error checking in sel_write_load()
    
    [ Upstream commit 42c773238037c90b3302bf37a57ae3b5c3f6004a ]
    
    Move our existing input sanity checking to the top of sel_write_load()
    and add a check to ensure the buffer size is non-zero.
    
    Move a local variable initialization from the declaration to before it
    is used.
    
    Minor style adjustments.
    
    Reported-by: Sam Sun <samsun1006219@xxxxxxxxx>
    Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
    [cascardo: keep fsi initialization at its declaration point as it is used earlier]
    [cascardo: keep check for 64MiB size limit]
    Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index e9eaff90cbccd..fd6282fa9c39f 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -535,6 +535,16 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf,
 	ssize_t length;
 	void *data = NULL;
 
+	/* no partial writes */
+	if (*ppos)
+		return -EINVAL;
+	/* no empty policies */
+	if (!count)
+		return -EINVAL;
+
+	if (count > 64 * 1024 * 1024)
+		return -EFBIG;
+
 	mutex_lock(&fsi->mutex);
 
 	length = avc_has_perm(&selinux_state,
@@ -543,23 +553,15 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf,
 	if (length)
 		goto out;
 
-	/* No partial writes. */
-	length = -EINVAL;
-	if (*ppos != 0)
-		goto out;
-
-	length = -EFBIG;
-	if (count > 64 * 1024 * 1024)
-		goto out;
-
-	length = -ENOMEM;
 	data = vmalloc(count);
-	if (!data)
+	if (!data) {
+		length = -ENOMEM;
 		goto out;
-
-	length = -EFAULT;
-	if (copy_from_user(data, buf, count) != 0)
+	}
+	if (copy_from_user(data, buf, count) != 0) {
+		length = -EFAULT;
 		goto out;
+	}
 
 	length = security_load_policy(fsi->state, data, count);
 	if (length) {
@@ -578,6 +580,7 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf,
 		"auid=%u ses=%u lsm=selinux res=1",
 		from_kuid(&init_user_ns, audit_get_loginuid(current)),
 		audit_get_sessionid(current));
+
 out:
 	mutex_unlock(&fsi->mutex);
 	vfree(data);