Re: [PATCH 1/2] exec: Restore EACCES of S_ISDIR execve()

From: Marc Zyngier
Date: Fri Aug 14 2020 - 04:15:21 EST

On 2020-08-14 00:17, Kees Cook wrote:
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@xxxxxxxxxx>
Fixes: 633fb6ac3980 ("exec: move S_ISREG() check earlier")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
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;
case S_IFBLK:
case S_IFCHR:

Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>

Jazz is not dead. It just smells funny...