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Date:   Thu, 13 Aug 2020 16:17:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Marc Zyngier <maz@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: [PATCH 1/2] exec: Restore EACCES of S_ISDIR execve()

The return code for attempting to execute a directory has always been
EACCES. Adjust the S_ISDIR exec test to reflect the old errno instead
of the general EISDIR for other kinds of "open" attempts on directories.

Reported-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/lkml/20200813151305.6191993b@why
Fixes: 633fb6ac3980 ("exec: move S_ISREG() check earlier")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/namei.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index 2112e578dccc..e99e2a9da0f7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2849,8 +2849,10 @@ static int may_open(const struct path *path, int acc_mode, int flag)
 	case S_IFLNK:
 		return -ELOOP;
 	case S_IFDIR:
-		if (acc_mode & (MAY_WRITE | MAY_EXEC))
+		if (acc_mode & MAY_WRITE)
 			return -EISDIR;
+		if (acc_mode & MAY_EXEC)
+			return -EACCES;
 		break;
 	case S_IFBLK:
 	case S_IFCHR:
-- 
2.25.1

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