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

[Greg Kroah-Hartman]

On Thu, Aug 13, 2020 at 04:17:22PM -0700, 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>
> Link: https://lore.kernel.org/lkml/20200813151305.6191993b@why
> 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;
>  		break;
>  	case S_IFBLK:
>  	case S_IFCHR:


Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxx>