linux-kernel - [PATCH 14/14] getcwd(2): clean up error handling

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Message-Id: <20210519004901.3829541-14-viro@zeniv.linux.org.uk>
Date:   Wed, 19 May 2021 00:49:01 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Jia He <justin.he@....com>, Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: [PATCH 14/14] getcwd(2): clean up error handling

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/d_path.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/fs/d_path.c b/fs/d_path.c
index 8a9cd44f6689..23a53f7b5c71 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -390,9 +390,11 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 	rcu_read_lock();
 	get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
 
-	error = -ENOENT;
-	if (!d_unlinked(pwd.dentry)) {
-		unsigned long len;
+	if (unlikely(d_unlinked(pwd.dentry))) {
+		rcu_read_unlock();
+		error = -ENOENT;
+	} else {
+		unsigned len;
 		DECLARE_BUFFER(b, page, PATH_MAX);
 
 		prepend(&b, "", 1);
@@ -400,23 +402,16 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 			prepend(&b, "(unreachable)", 13);
 		rcu_read_unlock();
 
-		if (b.len < 0) {
-			error = -ENAMETOOLONG;
-			goto out;
-		}
-
-		error = -ERANGE;
 		len = PATH_MAX - b.len;
-		if (len <= size) {
+		if (unlikely(len > PATH_MAX))
+			error = -ENAMETOOLONG;
+		else if (unlikely(len > size))
+			error = -ERANGE;
+		else if (copy_to_user(buf, b.buf, len))
+			error = -EFAULT;
+		else
 			error = len;
-			if (copy_to_user(buf, b.buf, len))
-				error = -EFAULT;
-		}
-	} else {
-		rcu_read_unlock();
 	}
-
-out:
 	__putname(page);
 	return error;
 }
-- 
2.11.0