Merge branch 'work.sysctl' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull in Christoph Hellwig's series that changes the sysctl's ->proc_handler
methods to take kernel pointers instead. It gets rid of the set_fs address
space overrides used by BPF. As per discussion, pull in the feature branch
into bpf-next as it relates to BPF sysctl progs.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200427071508.GV23230@ZenIV.linux.org.uk/T/

1 files changed, 29 insertions, 18 deletions

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index b6f5d459b087..df2143e05c57 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -539,13 +539,13 @@ out:
 	return err;
 }
 
-static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
+static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
 		size_t count, loff_t *ppos, int write)
 {
 	struct inode *inode = file_inode(filp);
 	struct ctl_table_header *head = grab_header(inode);
 	struct ctl_table *table = PROC_I(inode)->sysctl_entry;
-	void *new_buf = NULL;
+	void *kbuf;
 	ssize_t error;
 
 	if (IS_ERR(head))
@@ -564,27 +564,38 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
 	if (!table->proc_handler)
 		goto out;
 
-	error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count,
-					   ppos, &new_buf);
+	if (write) {
+		kbuf = memdup_user_nul(ubuf, count);
+		if (IS_ERR(kbuf)) {
+			error = PTR_ERR(kbuf);
+			goto out;
+		}
+	} else {
+		error = -ENOMEM;
+		kbuf = kzalloc(count, GFP_KERNEL);
+		if (!kbuf)
+			goto out;
+	}
+
+	error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
+					   ppos);
 	if (error)
-		goto out;
+		goto out_free_buf;
 
 	/* careful: calling conventions are nasty here */
-	if (new_buf) {
-		mm_segment_t old_fs;
-
-		old_fs = get_fs();
-		set_fs(KERNEL_DS);
-		error = table->proc_handler(table, write, (void __user *)new_buf,
-					    &count, ppos);
-		set_fs(old_fs);
-		kfree(new_buf);
-	} else {
-		error = table->proc_handler(table, write, buf, &count, ppos);
+	error = table->proc_handler(table, write, kbuf, &count, ppos);
+	if (error)
+		goto out_free_buf;
+
+	if (!write) {
+		error = -EFAULT;
+		if (copy_to_user(ubuf, kbuf, count))
+			goto out_free_buf;
 	}
 
-	if (!error)
-		error = count;
+	error = count;
+out_free_buf:
+	kfree(kbuf);
 out:
 	sysctl_head_finish(head);