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From:   Kees Cook <keescook@chromium.org>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        Eric Biggers <ebiggers3@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        linux-fsdevel@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/4] exec: Change uselib(2) IS_SREG() failure to EACCES
Date:   Sun, 17 May 2020 22:54:54 -0700
Message-Id: <20200518055457.12302-2-keescook@chromium.org>
In-Reply-To: <20200518055457.12302-1-keescook@chromium.org>
References: <20200518055457.12302-1-keescook@chromium.org>
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Change uselib(2)' S_ISREG() error return to EACCES instead of EINVAL so
the behavior matches execve(2), and the seemingly documented value.
The "not a regular file" failure mode of execve(2) is explicitly
documented[1], but it is not mentioned in uselib(2)[2] which does,
however, say that open(2) and mmap(2) errors may apply. The documentation
for open(2) does not include a "not a regular file" error[3], but mmap(2)
does[4], and it is EACCES.

[1] http://man7.org/linux/man-pages/man2/execve.2.html#ERRORS
[2] http://man7.org/linux/man-pages/man2/uselib.2.html#ERRORS
[3] http://man7.org/linux/man-pages/man2/open.2.html#ERRORS
[4] http://man7.org/linux/man-pages/man2/mmap.2.html#ERRORS

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/exec.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 06b4c550af5d..30735ce1dc0e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -139,11 +139,10 @@ SYSCALL_DEFINE1(uselib, const char __user *, library)
 	if (IS_ERR(file))
 		goto out;
 
-	error = -EINVAL;
+	error = -EACCES;
 	if (!S_ISREG(file_inode(file)->i_mode))
 		goto exit;
 
-	error = -EACCES;
 	if (path_noexec(&file->f_path))
 		goto exit;
 
-- 
2.20.1