AT_EXECFD gives access to the binary file even if
it is not readable (only executable).

Moreover it can be opened with flags and mode that are not the ones
provided by do_openat() caller.

And it is not available because loader_exec() has closed it.

To avoid that, use only safe_openat() with the exec_path.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/syscall.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index ddf09d7eb61a..0c80e9d68e28 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8263,8 +8263,7 @@ static int do_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, int
     };
 
     if (is_proc_myself(pathname, "exe")) {
-        int execfd = qemu_getauxval(AT_EXECFD);
-        return execfd ? execfd : safe_openat(dirfd, exec_path, flags, mode);
+        return safe_openat(dirfd, exec_path, flags, mode);
     }
 
     for (fake_open = fakes; fake_open->filename; fake_open++) {
-- 
2.37.3

Le 27/09/2022 à 14:43, Laurent Vivier a écrit :
> AT_EXECFD gives access to the binary file even if
> it is not readable (only executable).
> 
> Moreover it can be opened with flags and mode that are not the ones
> provided by do_openat() caller.
> 
> And it is not available because loader_exec() has closed it.
> 
> To avoid that, use only safe_openat() with the exec_path.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>   linux-user/syscall.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index ddf09d7eb61a..0c80e9d68e28 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -8263,8 +8263,7 @@ static int do_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, int
>       };
>   
>       if (is_proc_myself(pathname, "exe")) {
> -        int execfd = qemu_getauxval(AT_EXECFD);
> -        return execfd ? execfd : safe_openat(dirfd, exec_path, flags, mode);
> +        return safe_openat(dirfd, exec_path, flags, mode);
>       }
>   
>       for (fake_open = fakes; fake_open->filename; fake_open++) {

Applied to my linux-user-for-7.2 branch.

Thanks,
Laurent